Stripe

Sierra

Stripe

Stripe charges a flat 2.9% + $0.30 per transaction. That's it.

No setup fees, no monthly fees, no hidden charges. The simplicity is the product.

When a customer pays on a website using Stripe, Stripe handles everything — fraud detection, currency conversion, bank transfers, tax calculation, compliance. The merchant just sees money arrive in their account.

On top of the core payments, Stripe has built an entire financial infrastructure stack. Billing for subscriptions, Connect for marketplace payments, Atlas for incorporating a company, Issuing for creating virtual cards, Treasury for banking-as-a-service, and Radar for fraud prevention.

They're basically building the financial plumbing for the entire internet.

Sierra

Companies pay Sierra to run their customer service with AI agents instead of hiring rooms full of humans. The agent talks to your customers over chat.

It answers questions. It processes returns.

It updates subscriptions. Here is the clever part.

Sierra charges based on outcomes, not seats. Brands pay when the AI actually resolves a problem, not just for having the software installed.

That pricing is unusual. Most software charges a flat monthly fee no matter what.

Sierra only gets paid when the bot does the job.

Stripe

Patrick Collison was 19. His brother John was 17.

They had already built and sold a company — Auctomatic, an eBay auction tool — for $5 million while still teenagers in Limerick, Ireland. Patrick went to MIT, John went to Harvard, and they both dropped out because they had a better idea.

The idea was embarrassingly obvious in hindsight. In 2010, accepting payments on the internet was a nightmare.

You had to get a merchant account, negotiate with a payment processor, deal with a gateway provider, handle PCI compliance, and write thousands of lines of code. It took weeks or months.

The Collisons thought it should take five minutes.

They built a simple API — seven lines of code — that let any developer start accepting credit card payments immediately. No merchant account.

No paperwork. No phone calls with banks.

Just paste seven lines of code and you're in business. They originally called it /dev/payments, then changed it to Stripe in 2011.

Peter Thiel and Elon Musk — the PayPal mafia — were among the first investors. Sequoia and Andreessen Horowitz piled in soon after.

The Collisons had built exactly what every developer on Earth had been wishing for.

Sierra

Bret Taylor had already done the impossible twice. He co-created Google Maps.

He later became co-CEO of Salesforce, chaired Twitter's board during the messy Elon Musk takeover, and became chairman of OpenAI in late 2023. Clay Bavor spent 18 years at Google, most recently running its Labs group.

The two friends left their big jobs in 2023 to build something together. They picked customer service on purpose.

It is the least glamorous corner of software. Their logic was simple.

Companies hate their support costs. Customers hate waiting on hold.

AI that actually resolves problems could fix both sides at once. They launched Sierra in February 2024 with $110 million from Sequoia and Benchmark.

Stripe

Stripe grew almost entirely through developer love. They didn't hire a sales team for years.

They didn't run ads. They just built the best developer documentation anyone had ever seen and let word of mouth do the rest.

The developer-first strategy was deliberate. The Collisons realized that in a startup, the developer usually decides which payment provider to use.

If you make the developer happy, you win the company. Stripe's API documentation became legendary — clear, beautiful, with working code examples in every language.

They also grew by growing with their customers. Early Stripe customers included tiny startups that later became giants — Lyft, DoorDash, Instacart, Shopify.

As those companies scaled to billions in revenue, Stripe's processing volume scaled with them. Stripe didn't need to acquire new customers because its existing ones kept getting bigger.

The international expansion was methodical. Instead of launching everywhere at once like Uber, Stripe carefully added country after country, making sure each one worked perfectly with local payment methods, currencies, and regulations.

By 2024 they were letting businesses in dozens of countries take money from customers almost anywhere on earth, in 135 currencies.

Sierra

Sierra went straight for big brands, not tiny startups. SoFi, Ramp, ADT, Sonos and Brex signed up early.

By 2026 it said more than 40% of the Fortune 50 were customers. The trick was trust.

Enterprises are terrified of an AI bot going rogue and insulting a customer. So Sierra built guardrails and let each company control exactly how the agent behaves.

Bret Taylor's contacts did the rest. When the chairman of OpenAI calls a Fortune 500 CEO, they pick up.

Sierra hit $100 million in annual recurring revenue in November 2025, seven quarters after launch, and $150 million by February 2026. In April 2026 it launched Ghostwriter, which builds and deploys a new agent from a plain-English description.

Stripe

Valuation whiplash. In 2021, Stripe hit a peak valuation of $95 billion during the fintech boom.

By 2023, they had to mark it down to $50 billion during the tech correction — a 47% drop that made headlines everywhere. Employees who had been paper millionaires suddenly weren't.

The valuation has since recovered to $91 billion after a secondary share sale in 2025, but those two years were rough for morale.

Competition is relentless. Adyen, the Dutch payments company, has been eating into Stripe's enterprise market.

Square (now Block) competes on the small business side. PayPal is everywhere.

New fintech players pop up constantly. The payments business has razor-thin margins and everyone is fighting for the same 2.9%.

Going public is the elephant in the room. Stripe has been expected to IPO for years.

Investors, employees, and the media keep asking when. The Collisons have consistently said they're in no rush, but with $8.7 billion raised and thousands of employees holding stock options, the pressure to provide liquidity is enormous.

As of 2025, they've opted for secondary sales instead of a public offering.

Sierra

Everyone is building AI customer service agents right now. Decagon has raised at a multi-billion valuation.

Salesforce, ServiceNow and Intercom all shipped their own agents. Sierra is not the cheap option.

It sells premium AI to giant companies that move slowly. The bigger risk sits underneath the product.

Sierra does not make its own AI models. It rents them from providers like OpenAI and Anthropic.

If those model makers decide to compete directly, Sierra's edge gets thin fast, and its co-founder chairing one of them only makes that question louder. A $15.8 billion valuation on roughly $150 million in revenue leaves almost no room for a stumble.

Stripe

Stripe Payments is the core — accept credit cards, debit cards, Apple Pay, Google Pay, and 135+ payment methods in 195 countries. Stripe Connect lets marketplaces and platforms pay out to sellers (Shopify, Lyft, DoorDash all use it).

Stripe Billing handles subscription and recurring billing. Stripe Atlas lets you incorporate a US company from anywhere in the world — fill out a form, get a Delaware C-corp, bank account, and tax ID in days.

Stripe Radar uses machine learning to block fraud in real time. Stripe Treasury lets platforms offer banking services to their customers.

Stripe Tax automatically calculates and collects sales tax in every jurisdiction.

Sierra

The core product is the Sierra AI agent. It is a branded customer service bot that companies deploy on their website, app, and phone lines.

It handles the boring stuff. Order tracking.

Refunds. Password resets.

Account changes. Sierra also built its own tools to test and monitor these agents so they do not make things up.

In 2024 the company added a voice version that talks to customers on the phone. In April 2026 it added Ghostwriter, a tool that builds and deploys a new agent from a plain-English description.

The whole pitch is one AI agent that carries your brand's name and never sleeps.

Stripe

Peter Thiel, Elon Musk, Sequoia Capital, Andreessen Horowitz, General Catalyst, Founders Fund, Tiger Global, GV (Google Ventures), Goldman Sachs, Baillie Gifford

Sierra

Sequoia Capital and Benchmark wrote the first checks at launch in February 2024, $110 million between them. Greenoaks Capital then led both the $175 million round in 2024 and the $350 million round in September 2025.

In May 2026 Tiger Global and Google's GV led a $950 million round at a $15.8 billion valuation, with Benchmark, Sequoia and Greenoaks back in. That takes total funding to about $1.6 billion.

That is partly the product and partly Bret Taylor. Investors bet on founders who have already built billion-dollar things.