Flexprice
Open-source billing engine for usage-based and AI/agent pricing, with real-time metering, credits and automatic invoicing.
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Description
Charging by usage sounds simple until you actually have to build it: counting events as they happen, converting credits into dollars, handling a dozen currencies, generating tax-correct invoices, and doing all of that without double-charging anyone. Flexprice is a ready-made version of that machinery, built specifically for companies whose product is priced by how much AI or API usage a customer consumes rather than a flat monthly fee.
Flexprice is an open-source billing infrastructure platform aimed at AI-native and usage-based SaaS companies: it processes usage events in real time (10,000+ events/second, under 60ms at the 99th percentile), supports usage-based, credit-based and hybrid pricing models, and automates invoice generation, multi-currency conversion and tax handling. It connects to 50+ tools including Stripe, Razorpay, Snowflake and Google SSO, and is SOC 2 Type II compliant. Because the core engine is open source, it can be self-hosted instead of run purely as a hosted SaaS. Pricing starts free (100,000 events/month, capped at $100K cumulative revenue), then Build at $500/month (1M events, $250K cap), Scale at $1,000/month (5M events, $1.2M cap), and a custom on-premise tier with SAML SSO for larger deployments.
💬 Our review
The short version: Flexprice's pitch is usage-based billing without vendor lock-in — it's genuinely open source, so a team that wants full control over its billing data (or needs to self-host for compliance reasons) has a real option that closed-source competitors like Amberflo or Orb don't offer.
The revenue-capped free and Build tiers are the practical catch: at $100K and $250K cumulative revenue caps respectively, a fast-growing company will outgrow the cheap tiers quickly and land on the $1,000/month Scale plan or the custom on-premise deal, at which point the price gap with closed-source competitors narrows. Against Lago, the other well-known open-source billing engine, Flexprice's edge is speed (sub-60ms metering) and AI-specific credit-based pricing support; against Amberflo and Orb, the edge is self-hosting. For a team that specifically needs to self-host its billing engine, or is building AI-credit pricing from day one, Flexprice earns its place; for a team happy on a closed-source SaaS, Orb or Stripe Billing are simpler to just turn on.
💰 Pricing
📊 Global score
🤖 AI-enriched data
Free: 100k events/mo, $100K cumulative revenue cap. Build: $500/mo, 1M events, $250K cap. Scale: $1,000/mo, 5M events, $1.2M cap. Custom: on-premise, SAML SSO.
Pros
Genuinely open source — self-hostable, not just closed SaaS with a free tier
Sub-60ms, 10,000+ events/sec real-time metering
Native support for AI-style credit-based pricing, not just flat usage tiers
Cons
Free and Build tiers are capped by cumulative revenue, not just event volume
Fast-growing companies will hit the $1,000/mo Scale tier sooner than expected
Younger, smaller ecosystem than Stripe Billing or Orb