If your product charges for a stream of events instead of a flat seat price, tokens in and out, agent runs, GPU seconds, you need a meter that survives a customer disputing the invoice: dedupe the events, aggregate them into a period, price them against the contract. I went looking for who still builds that independently and found the market had consolidated hard in the last year. I wrote a longer version of this comparison on DevToolLab, with the full pricing script and a screenshot of every dashboard; this is the short version.
The Independent Shortlist Isn't Independent Anymore
In ten months, all three vendors most comparison posts point to got bought. Kong announced it was acquiring OpenMeter on September 3, 2025. Stripe closed its purchase of Metronome on January 14, 2026, for an undisclosed price that reporting puts near $1 billion. Adyen agreed to pay $335 million for Orb on June 11, 2026, closing July 1 and folding it in as an "indirect wholly owned subsidiary" under an incubator model. Orb's own homepage now reads "an adyen company."
A Metronome-run survey from January 2025 found 85% of 100 surveyed SaaS companies had already adopted usage-based pricing, so the timing tracks. Worth noting the survey came from a vendor selling the thing it measured, but the acquisitions back up the trend either way.
The Math: Percentage of Revenue vs a Fixed Bill
Only two platforms in this space publish a price without a sales call: Stripe Billing at 0.7% of billing volume, and Flexprice, whose top self-serve tier is $1,000 a month. Everything else routes to Contact Sales.
Run that 0.7% against a self-hosted budget and the crossover point is concrete. At $50,000 a month in billing volume, 0.7% is $350, cheaper than any engineer's time. But if running something like Lago or Kill Bill yourself costs $3,000 a month in infrastructure and attention, the percentage fee overtakes that around $429,000 a month in billing volume, roughly a $5.1M annual run rate. Below that line, pay the fee. Above it, the math flips toward self-hosting. The original post has the runnable script behind this table if you want to plug in your own volume and infra budget instead of these three examples.
Six Platforms, Verified This Month
Stripe Billing charges 0.7% of billing volume, pay as you go, with up to 100 million metering events a month included. Anything past basic metering, multidimensional rates, negotiated contracts, routes to a Contact Metronome button, since that is exactly where Metronome landed after the acquisition.
Orb, now under Adyen, is the pick for genuinely complicated pricing: hybrid plans, matrix rates, mid-period recomputation when a contract changes. Customers include Vercel, Replit, Supabase and LaunchDarkly, and ingestion is stress-tested to 250,000 events a second. There's no published price; it's billings plus events plus a platform fee, quote only.
Lago is the open-source option with the most AI-billing polish: AGPL-3.0, 10,593 GitHub stars, v1.53.0 shipped September 8, 2026. Free to self-host; Premium (prepaid credits, entitlements, customer portal) is quote-only, and AGPL is a hard no for some legal teams.
Flexprice is the rare open-source vendor with a real public price ladder: free up to 100,000 events a month, $500/month for 1 million events, $1,000/month for 5 million events and up to $1.2M in cumulative billing. AGPL-3.0, 6,201 stars, v2.1.31. Those ceilings are low for a real token-metered workload, and plans gate on cumulative rather than monthly billing, so once an account crosses a threshold it stays across it.
OpenMeter, an Apache-2.0 project now owned by Kong, is a metering layer rather than a full billing suite: 2,331 stars, still pre-1.0 at v1.0.0-beta.233. The managed path is now Kong Konnect.
Kill Bill is the oldest option here and argues hardest against paying a percentage forever: fixed cost, self-run, Apache-2.0, 5,753 stars, 15+ years in production and 100,000+ subscriptions claimed. It is also a Java platform with a plugin architecture, and the heaviest operational lift of the six.
Picking One Without Migrating Twice
Run the math on your own volume before reading another pricing page. Under roughly $200,000 a month in billing volume, Stripe's 0.7% usually beats the engineering cost of running your own meter. Above it, count events rather than revenue, since event volume is what actually breaks self-serve tiers. A product generating 40 million events a month is outside every self-serve plan here regardless of vendor.
If you already know you need open source, the license split matters more than the feature list: Lago and Flexprice are AGPL-3.0, OpenMeter and Kill Bill are Apache-2.0. And if you are leaning toward Orb, get the multi-PSP commitment from Adyen in writing before migrating. The incubator model is explicitly described as a first phase, not a permanent structure.
One practical note whichever you pick: idempotency keys are what stop a replayed usage event from being billed twice, and a UUID generator is a fast way to mint test ones while you build the ingestion path. And if you are trying to work out what a 0.7% revenue share actually leaves you per customer against a flat monthly fee, running the numbers through a margin calculator makes the comparison concrete before you commit to either model.
Conclusion
2026 changed ownership, not capability. Two payments companies and an API gateway company bought their way into metering inside ten months, and what is left independent is mostly open source: Lago, Flexprice, OpenMeter and Kill Bill, all usable, all with real tradeoffs. The question worth asking at renewal time is whether your billing cost is a percentage that keeps growing with your revenue, or a number you control.
References
- Best Usage-Based Billing Platforms 2026, DevToolLab - the full price simulation script, six dashboard screenshots and the side-by-side license and pricing table
- Stripe Billing pricing
- Orb
- Lago
- Flexprice
- OpenMeter
- Kill Bill
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