x402 is the HTTP 402 "Payment Required" extension Sella uses for machine-payable APIs. The first call returns 402 with payment instructions; the client signs and retries with a PAYMENT-SIGNATURE header, and the server settles on-chain in USDC before returning the response.

How is net revenue per call calculated?

Net = Gross price − Platform fee − On-chain gas. The Sella platform fee defaults to 5% and gas depends on the chosen chain. Stellar is the cheapest (~$0.00001/op), Base ~$0.003, Solana ~$0.00025.

Should I price below my cost to drive volume?

No. Every call would lose money. Use the break-even cells to see how many profitable calls you need to cover a fixed cost (server bill, API license). If profit per call is negative, raise price or reduce cost first.

Tools

x402 pricing estimator: margin, break-even, and chain comparison

Set your cost per call and target price. The calculator deducts the Sella platform fee and on-chain gas (Stellar, Base, or Solana), then shows net margin, monthly net revenue, and the call volume needed to break even on fixed costs.

Your cost per call (USD)

Price per call (USDC)

Monthly call volume

Payment chain

Platform fee (%)

Profitable per call

$0.0045 net / call

Margin: 45.0% · Net revenue per call: $0.0065

Gross / month

$1.00K

Net / month

$650.00

Profit / month

$450.00

Break-even volume for fixed costs

Cover $100

22,223 calls

Cover $1,000

222,223 calls

Cover $10,000

2,222,223 calls

Publish at this price →

How x402 pay-per-call pricing works

With x402 on Sella you set a flat USDC price per call. The protocol issues a 402 Payment Required on the first request and settles the agent's signed payment on-chain before returning the response. Your effective revenue per call is the gross price minus the marketplace platform fee and the chain's settlement gas. The cheaper the chain, the more you keep, but bridging, custody, and liquidity considerations matter too.

Pricing FAQ

What is x402?: x402 is the HTTP 402 "Payment Required" extension Sella uses for machine-payable APIs. The first call returns 402 with payment instructions; the client signs and retries with a PAYMENT-SIGNATURE header, and the server settles on-chain in USDC before returning the response.
How is net revenue per call calculated?: Net = Gross price − Platform fee − On-chain gas. The Sella platform fee defaults to 5% and gas depends on the chosen chain. Stellar is the cheapest (~$0.00001/op), Base ~$0.003, Solana ~$0.00025.
Should I price below my cost to drive volume?: No. Every call would lose money. Use the break-even cells to see how many profitable calls you need to cover a fixed cost (server bill, API license). If profit per call is negative, raise price or reduce cost first.

Sella, the economy for AI agents

Discover, preview, and pay for machine-payable datasets, evals, and APIs on the Sella marketplace. Or publish your own.