Block (Square)

Sierra

Block (Square)

Block makes money across several business lines. Square (the seller ecosystem) charges merchants a flat percentage per transaction — 2.6% + $0.10 for in-person payments, higher for online.

Cash App takes a fee on instant deposits, Bitcoin trading, and Cash App Pay transactions. Afterpay (announced at $29 billion in 2021, though Block's share price fell so far before closing in January 2022 that the final price was closer to $14 billion) earns merchant fees on buy-now-pay-later transactions.

TIDAL is the music streaming service (acquired from Jay-Z). Block also earns Bitcoin revenue — Cash App is one of the largest Bitcoin brokers in the US, though margins on BTC trading are razor-thin.

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.

Block (Square)

The origin story starts with Jim McKelvey, a glass blower in St. Louis and old friend of Jack Dorsey.

In 2009, McKelvey lost a $2,000 sale on a glass faucet because he couldn't accept credit cards. The customer wanted to pay with Amex.

McKelvey couldn't process it. The sale fell through.

McKelvey called Dorsey, who had been pushed out of the Twitter CEO job the year before and was serving as its chairman, and they started brainstorming. The problem was obvious: millions of small businesses, street vendors, farmers market sellers, and independent contractors couldn't accept credit cards because merchant accounts required monthly fees, credit checks, and clunky hardware that cost hundreds of dollars.

Dorsey and McKelvey wanted to make it so anyone could accept a credit card using just their phone.

They built a tiny white card reader that plugged into a smartphone's headphone jack. The reader cost almost nothing to manufacture and Square gave it away for free.

The software was simple — swipe the card, enter the amount, the customer signs on the screen, done. Square charged a flat 2.75% per transaction with no monthly fees, no contracts, and no minimums.

The product launched in 2010 and spread through small businesses like wildfire.

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.

Block (Square)

Square grew by giving away the hardware. The card reader was free.

That eliminated the biggest barrier for small businesses. A food truck operator, a yoga instructor, a farmers market vendor — anyone could start accepting cards in five minutes without spending a dollar upfront.

Square made its money on the transaction fees that followed.

The simplicity was the pitch. Traditional merchant services involved contracts, monthly minimums, tiered pricing, and hidden fees that required a finance degree to understand.

Square charged one flat rate for everything. No surprises.

That transparency built enormous trust with small business owners who had been burned by traditional processors.

Cash App grew through peer-to-peer payments and a brilliant viral strategy. The app launched in 2013 as a simple way to send money to friends.

Rappers, influencers, and content creators started using their $cashtag for tips and payments. Cash App sponsored hip-hop events and partnered with musicians.

By 2024, Cash App had over 55 million monthly active users — more than most banks.

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.

Block (Square)

The Afterpay acquisition was controversial. Announced at $29 billion in 2021, it closed in January 2022 at roughly half that after Block's own stock fell.

Buy-now-pay-later was already facing regulatory scrutiny and growing delinquency rates. Critics argued Dorsey overpaid at the peak of the market.

Afterpay's revenue growth slowed significantly after the acquisition, and write-offs on bad consumer debt increased. It remains the biggest bet Block has ever made.

The Bitcoin obsession worries investors. After renaming Square to Block in December 2021, Dorsey went all-in on Bitcoin — investing company cash in BTC, building Bitcoin mining hardware, and creating TBD (a Bitcoin-focused developer platform).

While Cash App's Bitcoin revenue is huge on paper ($10+ billion annually), the margins are tiny. Investors question whether the Bitcoin focus distracts from the core payments business.

Competition is intense on every front. Square competes with Stripe, Toast, and Clover for merchants.

Cash App competes with Venmo, Zelle, and Apple Pay for consumers. Afterpay competes with Klarna, Affirm, and bank-native BNPL products.

Block has to fight multiple wars simultaneously with finite resources.

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.

Block (Square)

Square is the merchant ecosystem — point-of-sale hardware, payment processing, invoicing, payroll, loans, and online stores for businesses of all sizes. Cash App is the consumer side — peer-to-peer payments, direct deposit, investing, Bitcoin buying, and the Cash App Card (a debit card).

Afterpay is the buy-now-pay-later product — split any purchase into four interest-free payments. Square Banking offers business checking accounts and loans.

Square Online lets merchants build e-commerce websites. TIDAL is the music streaming platform that pays artists higher royalties.

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.

Block (Square)

Khosla Ventures, Sequoia Capital, Kleiner Perkins, Visa, Goldman Sachs, GIC (Singapore)

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.