Function cost_micros 

pub fn cost_micros(provider_model: &str, usage: Usage) -> u64

The DW-079 pricing seam: micro-USD for one provider-model call with this usage. Reads prices through a DEFAULT (empty) pricing table, so this free function always returns 0 (the unknown-model allow policy) — it exists for test/backward-compat call sites that do not have a dataplane handle. The live path uses the dataplane’s compiled PricingTable (stored on the DataPlane as an ArcSwap, refreshed per generation).