The Cost Floor Collapsed — What to Re-Score, What to Ignore, and What to Ship This Sprint
Three Cost Drops Converged in One Week
DeepSeek-V4-Pro delivers GPT-5.5-comparable quality at 1/7th the cost, while V4-Flash is 98% cheaper than proprietary frontier models. GPT-5.5 itself shipped at 35x cheaper per-token than its predecessors. DeepSeek V4 is also 4x cheaper than GPT-5.4 for non-frontier use cases. These aren't incremental optimizations — they're category resets.
The math is concrete: a feature costing $0.80/user/month at Q1 pricing now runs at $0.02/user/month on DeepSeek-V4-Flash. A summarization feature killed because inference cost was seven cents per interaction is now two-tenths of a cent. The 1.6-trillion-parameter MoE architecture with a Hybrid Attention Architecture cuts KV cache memory by 90%, and the native 1M-token context window opens workflows that were architecturally impossible at 128k-256k.
The strategic question isn't 'is it good enough?' — it's 'what features can I now ship that I couldn't justify before?'
The Sorting Exercise That Matters
Not every shelved feature was shelved for cost. The critical exercise this sprint is a two-column sort: left column for features killed because inference cost exceeded willingness to pay, right column for features killed because the model was wrong too often, too slow, or produced output users didn't trust. The cost collapse moves items from the left column back into play. It does nothing for the right column.
GPT-5.5 and Claude Opus 4.7 still lead on pure reasoning benchmarks. But on the agentic BrowseComp benchmark, DeepSeek-V4-Pro-Max scored 83.4% — beating Claude Opus 4.7. For summarization, classification, extraction, generation, and agent orchestration, DeepSeek is functionally equivalent at a fraction of the price. DeepSeek-V4's tiered reasoning modes (Non-think, Think High, Think Max) let you match compute cost to task complexity per query — the kind of per-request optimization lever PMs need at scale.
The Architectural Investment Is No Longer Optional
You now have at minimum four frontier-class model families to consider: GPT-5.5, Claude Opus 4.7, DeepSeek-V4 (MIT, self-hostable), and Mistral Medium 3.5 (open weights, runs on 4 GPUs, 77.6% on SWE-Bench). Each has different prompting idioms, strengths, and cost profiles. OpenAI's official GPT-5.5 prompting guide explicitly tells developers to scrap legacy prompts and migrate JSON enforcement to the Structured Outputs API — signaling an architectural break. The PM investment is a model abstraction and routing layer that can benchmark across providers and swap without prompt rewrites. Teams locked into a single provider will iterate 3-5x slower than teams with routing flexibility.
A Caution on Timing
One source notes a PM who is "waiting to see if the price holds for sixty days" before acting. That instinct is correct for committing to a single provider, but wrong for the re-scoring exercise. The backlog audit costs nothing and should happen this sprint regardless of which provider's pricing you ultimately commit to. The features that were margin-negative at any price point above $0.05/interaction are now viable across multiple competing providers — that structural shift doesn't reverse.
What to do
Re-run unit economics on every AI feature killed for cost reasons in the last 4 quarters, using DeepSeek-V4-Flash pricing as the new floor. Rank by user value, not by revival cost.
Prototype one high-value feature using DeepSeek-V4's 1M-token context window that was architecturally impossible at 128k-256k. Scope by end of sprint.
Build or spec a model abstraction layer supporting GPT-5.5, Claude Opus 4.7, DeepSeek-V4, and Mistral Medium 3.5. Include per-query routing logic based on task complexity.
Update GPT-5.5 integration prompts per OpenAI's official guide: remove step-by-step scaffolding, migrate JSON schema to Structured Outputs API, use system prompts for persona.