GLM-5.3-Flash vs Gemini 3.7 Flash vs DeepSeek V4 Flash
The Short Answer
As of August 27, 2026, the cheap-tier decision is mostly about three things that are not benchmark scores: actual cost per task after peak/promo pricing, whether you need open weights, and whether you need multimodal input.
- GLM-5.3-Flash — cheapest, MIT weights, native video input. Pick this for raw volume.
- DeepSeek V4 Flash — cheap off-peak, doubles at peak, MIT weights, huge concurrency. Pick this if your traffic is off-peak and you need 2,500 concurrent.
- Gemini 3.7 Flash — most expensive of the three and API-only, but the most mature tooling and the strongest agentic scores. Pick this if reliability of the platform matters more than price.
Cost Per Task — The Number That Decides It
Reference task: 30,000 input tokens, 5,000 output tokens. Verified against PRICING-FACTS.md and vendor pricing pages on August 27, 2026.
| Model | Input / Output per MTok | Task cost | Notes |
|---|---|---|---|
| GLM-5.3-Flash (promo) | $0.075 / $0.25 | $0.0035 | Promo ends Sept 9, 2026 |
| GLM-5.3-Flash (standard) | $0.15 / $0.50 | $0.007 | Plan at this rate |
| DeepSeek V4 Flash (off-peak) | $0.22 / $0.66 | $0.0099 | 17h/day |
| DeepSeek V4 Flash (peak) | $0.44 / $1.32 | $0.0198 | 7h/day |
| Gemini 3.7 Flash (intro) | $0.75 / $3.75 | $0.041 | Intro ends Dec 31, 2026 |
| Gemini 3.7 Flash (2027) | $1.50 / $7.50 | $0.082 | From Jan 1, 2027 |
The spread is 23x between the cheapest realistic rate and the most expensive one. At a million tasks a month that is the difference between $7,000 and $82,000. This is not a rounding error and it is the single most under-modelled line in AI product budgeting.
Two traps in that table. GLM-5.3-Flash’s promo expires September 9, 2026 and Gemini 3.7 Flash’s intro expires December 31, 2026 — both will roughly double. Build your model on the post-promo column of both, or you will be re-forecasting in Q1 2027.
Specifications
| GLM-5.3-Flash | Gemini 3.7 Flash | DeepSeek V4 Flash | |
|---|---|---|---|
| Vendor | Z.ai | DeepSeek | |
| Released | Aug 26, 2026 | Aug 13, 2026 | 2026 (beta) |
| Architecture | 320B / 18B active MoE | Not disclosed | Not disclosed |
| Context | 1M | 1M | 1M |
| Max output | — | 65,536 | 384K |
| Multimodal | Image + video | Image, audio, video | Text-focused |
| Open weights | ✅ MIT | ❌ API-only | ✅ MIT |
| Concurrency | — | Google quota | 2,500 |
| Price stability | Promo to Sept 9 | Intro to Dec 31 | Peak/off-peak 2x |
GLM-5.3-Flash — The Price Leader
Released August 26, 2026, this is the newest of the three and the cheapest by a clear margin. 320B total parameters, 18B active per token, natively multimodal with image and video input, 1M context, MIT-licensed weights.
Independent positioning: Artificial Analysis Intelligence Index v4.1.1 score of 57 at about $0.045 per task on the discounted tier. Z.ai claims it approaches Claude Opus 4.8 on internal coding benchmarks — vendor-internal, so discount accordingly.
Choose it when: you are routing high volume, you want video input without a separate vision model, or you need permissively-licensed weights for compliance or an eventual self-host.
Skip it when: you need a mature enterprise support contract, or your workload is hard agentic coding where the frontier tier still wins decisively.
DeepSeek V4 Flash — Cheap, If Your Clock Cooperates
DeepSeek repriced at 16:00 UTC on August 16, 2026, moving from flat pricing to a peak/off-peak split. This is the detail that most comparisons get wrong.
Peak = 01:00-04:00 and 06:00-10:00 UTC (7 hours/day). Peak costs exactly double off-peak.
- US/EU business hours → mostly off-peak → $0.0099/task, genuinely competitive.
- Asia-Pacific business hours → mostly peak → $0.0198/task, more expensive than GLM-5.3-Flash even at standard rates.
Cache-hit pricing also moved sharply: $0.007 off-peak and $0.014 peak, up from $0.0028 flat. If your architecture leaned on cheap cache hits, re-run the numbers.
What DeepSeek still wins on: 384K max output and 2,500 concurrency, both best-in-class here. For bulk batch generation that is a real operational advantage.
Never quote a single flat DeepSeek price. It has not been flat since August 16, 2026.
Gemini 3.7 Flash — Expensive, But the Grown-Up Option
Released August 13, 2026 at $0.75/$3.75 — a 50% intro rate running through December 31, 2026, reverting to $1.50/$7.50 on January 1, 2027.
It is roughly six times GLM-5.3-Flash per task today, and twelve times from January. What you get for that: the strongest reported agentic gains of the three (FrontierCode 1.1 moved 34.4% → 43.6%, AutomationBench 17.0% → 30.4% versus 3.6 Flash), a genuinely mature multimodal stack, and Google Cloud’s operational surface — SLAs, regional endpoints, IAM, billing that an enterprise finance team recognises.
Choose it when: the platform matters more than the invoice, or you are already inside Google Cloud and the integration cost of adding a second vendor exceeds the savings.
Skip it when: you are cost-optimising volume, or you need weights.
The Decision, Compressed
| Your situation | Model |
|---|---|
| Maximum volume, minimum cost | GLM-5.3-Flash |
| Need MIT weights / self-host path | GLM-5.3-Flash or DeepSeek V4 Flash |
| Video or image input, cost-sensitive | GLM-5.3-Flash |
| Bulk generation, huge outputs, off-peak traffic | DeepSeek V4 Flash |
| Asia-Pacific business hours | GLM-5.3-Flash (DeepSeek peak kills it) |
| Enterprise SLA, GCP shop | Gemini 3.7 Flash |
| Hard agentic coding | None of these — escalate to frontier |
The pattern that beats picking one: route by difficulty. Send the routine 90% to GLM-5.3-Flash, escalate the hard remainder to Claude Opus 5 or GPT-5.6 Sol. A blended pipeline at $0.007 + occasional $0.275 beats a uniform $0.041 by a wide margin, and it beats a uniform frontier bill by an absurd one.