Price Index Delta: DeepSeek Doubles, Kimi K3 Splits, gpt-oss Reverts

The fourth DeAI Price Index observation is dated 2026-10-05 UTC, two weeks after issue three (no observation ran on 2026-09-28 — see Background). Comparing OpenRouter's public catalog against the 2026-09-21 snapshot, the headline move is deepseek-v4.1-flash, up 100% to $0.30 input / $1.20 output per million tokens — the aggregator row now lists DeepSeek's official peak rate — while Moonshot AI's Kimi K3 split its spread: input down 61% to $0.67, output up 65% to $14.00.

Key facts

• DeepSeek V4.1 Flash on OpenRouter: $0.15/$0.60 → $0.30/$1.20 (+100%) — the row moved from the off-peak rate to the official peak rate, which is unchanged. Fireworks separately raised its own DeepSeek V4.1 Flash serverless pricing Oct 1, nearly doubling output cost.
• Kimi K3 on OpenRouter: $1.70/$8.50 → $0.67/$14.00 (input -61%, output +65%) — a 21× input/output spread, observed 2026-10-05 on the OpenRouter models API. This is an aggregator row, not an official Moonshot price.
• DeepSeek V4 Pro (0423) on OpenRouter: $0.9553/$1.9105 → $0.2088/$0.4176 (-78%) — while the sibling deepseek-v4-pro-0813 row lists $4.50/$5.00 and the ~deepseek/deepseek-pro-latest alias $1.901/$4.20.
• gpt-oss-120b: $0.15/$0.60 → $0.037/$0.17 — reverted to the value observed on 2026-09-07 and 2026-09-14, confirming the 2026-09-21 reading flagged in issue three as a catalog data revision, not a price move.
• GLM-5.3 Flash: $0.09/$0.30 → $0.15/$0.50 (+67%) — back to its 2026-09-14 level; full-size GLM-5.3 blew out to $0.05 in / $7.00 out (input -95%, output +145%).
• Hermes 4 70B is still absent from the OpenRouter catalog — the third consecutive observation without it. nousresearch/hermes-4-405b remains listed.

What happened

Ten of the seventeen tracked rows moved week-over-week against the 2026-09-21 baseline, and for the first time in four observations the biggest mover is an increase. The deepseek-v4.1-flash row doubled to $0.30/$1.20. That figure is not new: it is exactly DeepSeek's official peak cache-miss rate, re-verified unchanged on DeepSeek's own pricing page today (off-peak $0.15/$0.60, peak $0.30/$1.20, cache-hit input $0.003 off-peak / $0.006 peak, peak hours 01:00–04:00 and 06:00–10:00 UTC Monday–Friday). Issue three caught the row listing off-peak pricing on a Monday; issue four catches it listing peak pricing. The practical read for builders: this row tracks the peak/off-peak schedule, and which rate you see depends on when you look.

The timing is notable. On October 1, Fireworks raised its own DeepSeek V4.1 Flash serverless pricing — Standard tier from $0.22 input / $0.66 output to $0.30 / $1.20 per million tokens, nearly doubling output cost, "to bring our pricing in line with current market rates." OpenRouter's row now lists the same $0.30/$1.20 figures. We cannot attribute intent from a catalog row, but two independent surfaces moving to identical numbers within four days is the closest thing to a market repricing this basket has produced.

The Kimi K3 row tells the week's second story: a scissors move. Input fell 61% to $0.67 while output rose 65% to $14.00 — a 21× input/output spread, the widest in the basket. Issue three recorded Kimi K3's 36% cut; this week's shape suggests the aggregator's backend mix changed rather than Moonshot rewriting a price card. At $0.67 input it is now cheaper than Claude Sonnet 4.6 ($3.00/$15.00) on input but more expensive on output; the cheapest open-weight input row is now deepseek/deepseek-v4-flash-0731 at $0.0152.

The gpt-oss-120b flag, resolved

The data-quality flag from issue three is now closed. openai/gpt-oss-120b listed $0.037/$0.17 on 2026-09-07 and 2026-09-14, $0.15/$0.60 on 2026-09-21, and back to $0.037/$0.17 today — exactly the reversion the flag anticipated. The 2026-09-21 reading was a catalog artifact, and the index's decision to record and flag rather than average it away is what makes the series interpretable. Downstream derivatives should treat the 2026-09-21 gpt-oss row as noise.

Why it matters

• Peak/off-peak now visibly oscillates in aggregator rows. A builder pricing a workload off the OpenRouter catalog on a Monday morning will read a different rate than one checking Friday night. For DeepSeek V4.1 Flash the swing is 2×, and cache-hit input ($0.003–$0.006) is 25–50× cheaper than cache-miss — time-of-day and cache-hit ratio now swing effective cost more than any list move this week.
• Fireworks' hike may be the first of a wave. The week-ahead brief flags Fireworks' Oct 1 move as the pricing baseline other providers may follow. If OpenRouter's deepseek rows track official peak rates, the cheapest frontier-quality tier just doubled for peak-hour workloads.
• Aggregator rows remain unusable as official prices. Three DeepSeek "Pro" routes now list $0.2088/$0.4176 (0423), $4.50/$5.00 (0813) and $1.901/$4.20 (alias) simultaneously — a 21× spread under one brand. The checkpoint-portability rule from issue one applies: verify against the first-party page before committing spend.

Background

The DeAI Price Index is a weekly, dated, append-only observation of list pricing — it records what a catalog listed on a date, and never rewrites prior issues. Issue one established the basket and methodology: OpenRouter's GET /api/v1/models prompt/completion fields converted to dollars per million tokens, batch rows excluded, plus first-party anchors. Issue two covered the DeepSeek V4.1 Flash launch week; issue three caught the catalog moving down.

One process note: there was no 2026-09-28 observation — the scheduled Monday run did not produce a snapshot that week, so this issue compares against 2026-09-21 across a two-week gap. That gap makes the DeepSeek doubling harder to date precisely: it could have landed any time between September 22 and October 5. This is recorded rather than smoothed over. Also per the standing gap report: the automated DIPT pricing fetcher again produced no d_pricing candidates in this week's sweep (0 in data/tracker/{candidates,resolved}_2026-10-05.json), so the snapshot was fetched directly for this job using the documented Issue-1 methodology — the third week running without a wired OpenRouter adapter. The raw pull is dated and archived (data/tracker/pricing_fetch_2026-10-05.json); nothing here derives from provider marketing claims.

What's next

The next observation is scheduled for Monday, 2026-10-12. Watch items: whether the deepseek-v4.1-flash row flips back to off-peak later in the week (the schedule test), whether Kimi K3's scissors shape holds or normalizes, whether other providers follow Fireworks' hike, whether Hermes 4 70B returns, and whether the DIPT OpenRouter adapter gets wired so the snapshot stops depending on manual fetches. The machine-readable snapshot updates at /data/prices.json alongside this story, with the 2026-09-21 snapshot preserved in the file's archive chain.