A payments company paid a reported $7 billion for the layer that counts AI usage, seven months after buying the layer that invoices it. Routing was never the scarce asset — the scarce asset is one normalised record of what every model call cost and who it was for, and if that record lives in your request path you are paying a percentage on every step your agents take.
These four advertise time-to-first-audio between 40 and 200 ms, and an independent harness measures their cloud medians at 188 to 313 ms — but the number that breaks a phone call is the spread, not the median, and one vendor's jitter is nearly four times another's. Price moves about 2.5× across the field and predicts neither. The tail is bought with deployment.
These four price a search between $1 and $16 per thousand, and the spread is not margin — it is how far down the retrieval pipeline each one reads. Price a whole research turn instead of a call and the ordering inverts: the cheapest rate card produces a turn costing three times the dearest one.
The standard rate is $1.50 / $7.50 per million tokens, exactly what 3.6 Flash already listed at. What shipped on 13 August is a better model at the same list price with a discount that expires on 31 December — a known, dated 2× step in unit cost, landing on whatever trajectories you tuned while it was cheap.
A chat product needs several hundred concurrent users before a dedicated GPU beats per-token pricing; an agent needs about a dozen workers, because it re-sends its whole context every step. That arithmetic — not the price per million tokens — is what should decide which of these four you build on.
KPMG found 49% of leaders scaled back an agent deployment over cost and 7% report established ROI — so nine in ten of the organisations that cut did it without a denominator. Cost is metered by a vendor that needs to bill you; value stays at zero until someone builds it. The measurement you cannot add later is the pre-agent baseline.
Two of the four bill the agent loop at about nine cents per vCPU-hour and their prices are 3.6% apart; the other two do not charge for it at all. What each is actually selling is a place to keep the conversation — and AWS closing Bedrock Agents Classic to new customers on 30 July 2026 is the clearest evidence yet about which half of a managed runtime you can afford to rent.
A reranker touches no index and holds no state, so swapping one is an afternoon — which finally makes chasing the leaderboard rational, except the leaderboard measures the axis where these four differ least. What differs by more than an order of magnitude is the billing unit and the licence, and both bite hardest at agent scale.
Swapping your LLM edits a prompt. Swapping your embedding model re-embeds the corpus, rebuilds the index and invalidates every retrieval number you have — vectors from two models are not comparable, so there is no gradual migration. That makes this the one choice in a RAG stack you make under lock-in, and the deciding numbers are bytes per vector and who controls the model lifecycle, not a leaderboard rank.
Every comparison of these four opens with tokens per second on a fixed batch — the one number that transfers worst to agent traffic, where the same prompt comes back twenty times with a few hundred tokens appended. What separates them is what the KV cache is keyed on, whether constrained decoding survives a full batch, and how much of your quarter the build step eats.
Every document-parser comparison is published as an accuracy leaderboard, and accuracy is the axis that transfers worst to your documents. Two things do transfer: a layout pipeline can drop a number but cannot invent one, and the cost curves of self-hosted and hosted parsing cross at a volume you can compute in five minutes.
Every AI gateway sells the same headline feature: automatic failover to a second provider. That feature is not an availability win — it is an untested deploy that fires only during an incident, onto a model your evals never covered. Choose instead on who operates the hop, because that is the decision you cannot reverse cheaply.
List prices for agent search APIs cluster tightly around $5–8 per thousand queries, which makes the sticker the least interesting number in the comparison. What actually differs by an order of magnitude is how many tokens each one dumps into your context per result — and in an agent loop that re-sends its transcript every step, that is the bill.
Moonshot released 2.8 trillion parameters as a free download on 27 July — and priced its own API above the model it replaced, while no single GPU on the market can hold the weights. Open weights buy agent builders exactly one thing that closed APIs cannot, and it is not cost.
Every coding agent leaves a different telemetry trail — JSONL transcripts, a SQLite store, or only a prose log — so the open-source tracker worth installing depends on which trail your agent leaves. Four trackers, four trails, plus the levers that actually cut the bill.