DeepSeek V4 Flash vs GPT-5.6 Luna
DeepSeek against OpenAI, costed on the same three workloads. DeepSeek V4 Flash is cheaper on all three workloads.
Monthly bill, side by side
| Workload | DeepSeek V4 Flash | GPT-5.6 Luna | Difference |
|---|---|---|---|
| Support chatbot 2,500 six-turn conversations a day |
$394 | $887 | $493 (2.3×) |
| Document summariser 1,000 single-shot summaries a day |
$57.96 | $102 | $44.04 (1.8×) |
| Coding agent 200 twelve-turn sessions a day |
$318 | $598 | $280 (1.9×) |
No prompt caching and no batch discount on either side, so the comparison is like for like. Both figures assume 30 days a month.
The rate cards
| DeepSeek V4 Flash | GPT-5.6 Luna | |
|---|---|---|
| Input, per 1M tokens | $0.14 | $0.2 |
| Output, per 1M tokens | $0.28 | $1.2 |
| Cached input | $0.0028 | $0.02 |
| Context window | 1M | 1.05M |
| Maximum output | 8K | 128K |
| Reasoning model | yes | yes |
| Vision | no | yes |
Run this comparison on your own numbers
Full detail: DeepSeek V4 Flash pricing · GPT-5.6 Luna pricing