Slack

OpenAI

Slack

Slack uses a freemium model. The free tier gives you access to your most recent 90 days of messages and 10 app integrations.

That's enough to get hooked. Then Slack charges per user per month — $8.75/month for Pro, $15/month for Business+, and custom pricing for Enterprise Grid.

The beauty of the model is that one person signs up, invites their team, the team gets addicted, and suddenly the company is paying for 500 seats. It's a virus that charges rent.

OpenAI

OpenAI makes money primarily through API access and subscriptions. The API charges developers per token (roughly per word) for using GPT models in their applications.

ChatGPT Plus costs $20/month for individual users, ChatGPT Team is $25-30/user/month, and ChatGPT Enterprise is custom-priced. Microsoft pays OpenAI licensing fees and also resells OpenAI models through Azure OpenAI Service.

OpenAI's annualised revenue ran past $13 billion during 2025 and kept climbing from there, which is the kind of growth curve that normally only exists in a pitch deck.

Slack

Stewart Butterfield had already done this exact thing once before. In 2002, he was building a massively multiplayer online game called Game Neverending.

The game flopped but one of its features — a photo-sharing tool — became Flickr, which Yahoo bought for $35 million in 2005.

So in 2009, Butterfield did it again. He started a company called Tiny Speck to build another game called Glitch — a quirky, non-violent MMO where players collaborated instead of fighting.

The game was beautiful, weird, and a complete commercial failure. It shut down in November 2012 after never finding a big enough audience.

But the internal communication tool the Glitch team had built for themselves was something special. They had created a searchable, organized messaging system because email was driving them insane.

Every conversation was in channels. Everything was searchable.

Files were shared inline. It was everything email should have been but wasn't.

Butterfield looked at this internal tool and thought: this is the actual product. In August 2013, Slack launched in preview.

Within 24 hours, 8,000 companies had signed up. Within two weeks, it was 15,000.

The growth was so fast that Butterfield said it felt like "trying to drink from a fire hose."

OpenAI

OpenAI was founded in December 2015 as a nonprofit AI research lab. The founding donors — including Elon Musk, Sam Altman, Peter Thiel, Reid Hoffman, and Jessica Livingston — pledged $1 billion with a mission to build artificial general intelligence (AGI) that would benefit all of humanity.

The idea was that AI was too important and too dangerous to leave in the hands of Google alone.

Sam Altman became chairman while Greg Brockman (former CTO of Stripe) became president. Ilya Sutskever, one of the most respected AI researchers alive, left Google Brain to become chief scientist.

The early team was stacked with world-class researchers who published their work openly — hence "Open" AI.

But AI research turned out to be staggeringly expensive. Training large models required millions of dollars in compute.

In 2019, OpenAI created a "capped-profit" subsidiary — investors could earn up to 100x their money, but profits beyond that would flow to the nonprofit. Microsoft invested $1 billion.

The mission was still to save humanity. The method now involved making a lot of money first.

Slack

Slack grew almost entirely bottom-up. Nobody sold Slack to companies.

Employees adopted it on their own and then convinced their bosses to pay for it. One developer would start using the free version, invite their team, and within weeks the whole department was hooked.

IT departments would discover that half the company was already on Slack before anyone asked for approval.

The integrations strategy was genius. Slack made it dead simple for other software tools to plug into Slack.

Instead of checking Jira for bug reports, Salesforce for deals, and GitHub for code changes, everything pushed notifications into Slack. Slack became the operating system of work — the one app you kept open all day.

Word of mouth was the main growth driver. Slack didn't spend heavily on advertising early on.

They spent on making the product feel delightful. The loading messages were funny.

The emoji reactions were addictive. The search actually worked.

People genuinely liked using it, which is almost unheard of for enterprise software.

OpenAI

ChatGPT's launch in November 2022 was the growth strategy — it just wasn't planned that way. The team expected a modest research preview.

Instead, ChatGPT hit 1 million users in 5 days and 100 million monthly active users in 2 months, making it the fastest-growing consumer application in history. The product went viral because it felt like magic — for the first time, anyone could have a natural conversation with a machine that seemed to understand them.

The Microsoft partnership provided distribution at massive scale. Microsoft integrated OpenAI models into Bing, Office 365 (Copilot), GitHub (Copilot), and Azure.

Overnight, hundreds of millions of Microsoft users had access to OpenAI technology. Microsoft's $13 billion investment was the largest AI bet in history and gave OpenAI nearly unlimited compute.

The API created an ecosystem. Thousands of startups built products on top of OpenAI's models — from customer service bots to coding assistants to content generators.

Each API customer locked themselves into OpenAI's ecosystem, creating switching costs and recurring revenue.

Slack

Microsoft Teams was the existential threat. When Microsoft bundled Teams for free with Office 365 in 2017, Slack knew it was in trouble.

Microsoft had 300 million Office users who could start using Teams without paying anything extra. Slack even took out a full-page newspaper ad welcoming Microsoft to the chat market — a bravado move that masked genuine fear.

By 2020, Teams had overtaken Slack in daily active users purely on distribution.

The pandemic was a double-edged sword. Remote work exploded demand for Slack, but it also exploded demand for Teams, Zoom, and every other collaboration tool.

Slack's growth accelerated but so did everyone else's. The window where Slack was the obvious default was closing.

Revenue growth started slowing. After years of 50%+ annual growth, Slack's growth rate dropped to the low 30s by 2020.

Wall Street punished the stock, which dropped from its IPO price. The writing was on the wall — Slack couldn't outrun Microsoft alone.

In December 2020, Salesforce announced it was acquiring Slack for $27.7 billion. Butterfield stayed on as CEO until 2023, then left.

OpenAI

The board crisis of November 2023 nearly destroyed the company. The nonprofit board fired Sam Altman as CEO on a Friday, citing a loss of confidence.

Within 48 hours, 95% of employees threatened to quit and follow Altman to Microsoft. By Tuesday, Altman was reinstated and the board was restructured.

The incident exposed the fundamental tension between OpenAI's nonprofit governance and its for-profit ambitions — a tension it finally addressed in late 2025 by restructuring the business as a public benefit corporation sitting under the original nonprofit.

The cost of training frontier models is eye-watering. Each new GPT generation costs hundreds of millions to train.

OpenAI is reportedly spending over $7 billion annually on compute. The company is burning through cash faster than almost any startup in history, which is why it keeps raising at higher and higher valuations.

If revenue growth slows before costs stabilize, the math gets ugly.

Safety concerns are not going away. Multiple prominent researchers have left OpenAI over disagreements about the pace of development versus safety research.

Ilya Sutskever, the chief scientist who was central to the board's decision to fire Altman, left in 2024 to start a safety-focused AI lab. The public debate about whether OpenAI is moving too fast — and whether its safety commitments are genuine — grows louder with every capability improvement.

Slack

Slack is the core messaging platform — channels for teams, direct messages, threads for focused discussion, and huddles for quick voice/video calls. Slack Connect lets you message people at other companies directly through Slack instead of email.

Slack Canvas is a built-in document editor for notes and wikis right inside channels. Workflow Builder lets non-technical users automate repetitive tasks without writing code.

The App Directory has 2,600+ integrations — connect Google Drive, Salesforce, Jira, GitHub, or basically any tool your company uses.

OpenAI

ChatGPT is the consumer chatbot — the product that made AI mainstream overnight. The flagship GPT models are multimodal, handling text, images, and audio in one system.

The OpenAI API lets developers integrate GPT into any application. DALL-E generates images from text descriptions.

Whisper transcribes and translates audio. Sora generates videos from text prompts.

GPT Store lets users create and share custom GPT agents. ChatGPT Enterprise gives businesses a private, secure version of ChatGPT with admin controls and no data training.

Slack

Accel Partners, Andreessen Horowitz, Social Capital, GV (Google Ventures), SoftBank, Dragoneer Investment Group

OpenAI

Microsoft ($13B), Thrive Capital, Khosla Ventures, Sequoia Capital, Founders Fund, Tiger Global, SoftBank, a16z