When you line up DeepSeek’s V4‑Flash against OpenAI’s GPT‑5‑Nano, the first thing that jumps out is how the input bill differs by a few cents while the output bill swings dramatically. DeepSeek charges $0.0668 per 1M input tokens, $0.0134 per 1M cached input tokens and $0.1336 per 1M output tokens. OpenAI’s GPT‑5‑Nano asks $0.05 per 1M input tokens, $0.005 per 1M cached input tokens and $0.4 per 1M output tokens. In a scenario where you feed a model 10 M input tokens and get back 10 M output tokens, DeepSeek’s raw input cost is modestly higher, but its output cost is roughly a third of OpenAI’s. That asymmetry matters if your workload is output‑heavy, such as long‑form generation or summarisation.
### What you pay per token
| Vendor | Model | Input | Cached input | Output |
|--------|-------|-------|--------------|--------|
| DeepSeek | deepseek‑v4‑flash | $0.0668 per 1M tokens | $0.0134 per 1M tokens | $0.1336 per 1M tokens |
| OpenAI | gpt‑5‑nano | $0.05 per 1M tokens | $0.005 per 1M tokens | $0.4 per 1M tokens |
### Where the savings hide
DeepSeek’s advantage lives in the output tier. If your application churns out more tokens than it consumes, the lower $0.1336 output price can translate into a substantially lighter bill than OpenAI’s $0.4 rate. Conversely, if you run a cache‑friendly pipeline that reuses many prompt fragments, DeepSeek’s $0.0134 cached‑input fee still outpaces OpenAI’s $0.005, but the gap is narrower than the output disparity. For developers who need a balanced cost profile—moderate input, heavy output—DeepSeek V4‑Flash feels like the more economical choice. If you are building a low‑output, high‑precision prototype where every cached token matters, OpenAI’s cheaper cached‑input rate and the brand‑recognised safety guardrails of GPT‑5‑Nano may justify the higher output spend.
For startups racing to ship a product, the lower output price of DeepSeek can keep the burn rate in check while still delivering comparable latency. Enterprises that prioritize OpenAI’s ecosystem, tooling, and compliance certifications might accept the steeper output bill in exchange for the broader platform support. In short, DeepSeek wins on raw token economics for output‑heavy workloads, while OpenAI remains attractive for cache‑centric, compliance‑driven projects. Pricing verified on 2026-09-12.