RTX 5090 vs 4090 inference cost benchmark: Is spending 40% more justified?

TL;DR — Straight-to-the-point answerPure inference for 7B–13B models:The 4090 still dominates the 5090 on value for money—The 5090 is 30%–40% faster than the 4090, but rental costs are 40%–60% higher, resulting in higher per-thousand-token cost. Only two scenarios justify using the 5090: ① Strict 32GB VRAM requirement (e.g., 13B FP16 or 70B INT4 inference); ② Time-critical load testing or pre-launch validation.

Parameter Ledger

• RTX 4090: 24 GB GDDR6X, memory bandwidth 1.0 TB/s, FP16 performance ≈ 83 TFLOPS
• RTX 5090: 32 GB GDDR7, memory bandwidth 1.8 TB/s, significantly improved FP16/FP8 performance

Inference is bandwidth-intensive: RTX 5090’s 80 % bandwidth increase delivers tangible gains, yet measured token throughput for a 7B model shows only ~30–40 % improvement (as decoding becomes bottlenecked by other factors before bandwidth saturation).

How to calculate cost per 1,000 tokens

The formula is simple:Hourly rental fee ÷ hourly token outputTaking vLLM deployment of a 7B model as an example: RTX 4090 throughput ≈ 2000–3000 tokens/s; RTX 5090 ≈ 2800–4000 tokens/s. Factoring in real-time rental rates:

Rough cost estimate at current prices: ~¥0.2–0.35 per million tokens for RTX 4090, ~¥0.28–0.45 for RTX 5090.Pure economic analysis favors the RTX 4090。

When the RTX 5090 Becomes More Cost-Effective

• 13B FP16 inferenceModels ≥26GB exceed the 24GB VRAM of an RTX 4090—requiring quantization (with accuracy loss) or upgrading to a pricier A100. The RTX 5090’s 32GB VRAM fits such models perfectly, making it the most cost-effective viable option.
• 70B INT4 quantization: Even with ~40 GB VRAM, full loading fails—but extreme Q2/Q3 quantization within 30 GB is feasible—only possible on 32 GB GPUs.
• Limited-time tasksYou discover two hours before a client demo that benchmarks must be re-run—RTX 5090’s 40% speed advantage saves 40% time, where time is more valuable than rental cost.

Conclusion

Individual users and small-to-medium teams running 7B/8B inference:RTX 4090—no-brainer choiceOnly consider the 5090 when your model exceeds the 24GB VRAM threshold. Prices fluctuate in real time—check the live table above (updated hourly) before ordering, and rent from whichever provider offers the best rate. Some links include affiliate commissions, which do not affect ranking.