Subscription vs API vs GPUs
One fully used ChatGPT Pro 20x seat implies a monthly token volume. This calculator prices that same volume five ways: the subscription sticker, the GPT-5.6 Sol API, the DeepSeek-V4.1-Flash API, GPUs you buy, and GPUs you rent.
Rates as of September 28, 2026.
Monthly cost by path
Every path serves the same implied volume: 1.39B tokens a month, valued at $8,000 on GPT-5.6 Sol promotional rates.
- ChatGPT Pro 20x sticker1 seat at $200$200
- GPT-5.6 Sol APISame volume at promotional rates$8,000
- DeepSeek-V4.1-Flash APISame volume at blended rates$304
- Home hardware3x NVIDIA GeForce RTX 5090 over 24 months, 24/7$843$14,700 up front
- Rented GPUs3x NVIDIA GeForce RTX 5090 at $0.53/hr, 24/7$1,161
At list rates ($5/$30 per 1M), the same volume costs $11,389. DeepSeek off-peak $252, peak $503, blended $304.
Own or rent the same throughput
Dense ~32B (Q4-FP8) at about 45 decode tok/s per unit. The load needs 106 aggregate tok/s across 731 hours a month.
- Buy 3x NVIDIA GeForce RTX 5090$613 depreciation + $231 electricity$843$14,700 up front
- Rent 3x NVIDIA GeForce RTX 50903 units for 731 h/month$1,161
Depreciation Electricity Rental
Owning depreciates the $14,700 purchase straight-line over 24 months to a 0% resale value, plus grid electricity at 18.3¢/kWh. Set the electricity knob to the energy rate on your utility bill or a public tariff sheet; the presets span cheap hydro to island rates.
Ownership cost over the useful life
Cumulative cost of owning at each quarter of the 24-month useful life. Owning accrues $20,237 by the end; renting the same throughput accrues $27,876.
- Month 6$6,969 rented over the same months$5,059
- Month 12$13,938 rented over the same months$10,119
- Month 18$20,907 rented over the same months$15,178
- Month 24$27,876 rented over the same months$20,237$14,700 up front
Depreciation Electricity
Where the Sol API dollars go
- Input, cache miss556M tokens at $4/1M$2,222
- Input, cache hit556M tokens at $0.4/1M$222
- Output278M tokens at $20/1M$5,556
Implied load
| Monthly tokens | 1.11B in + 278M out = 1.39B |
|---|---|
| Required decode rate | 106 tok/s aggregate (24/7) |
| Home fleet | 3x NVIDIA GeForce RTX 5090 ($14,700 up front) |
| Rental fleet | 3x NVIDIA GeForce RTX 5090 at $0.53/hr |
| Throughput basis | Bandwidth estimate (Enverge DGX Spark prefill-versus-decode analysis (bandwidth method)) |
Single-stream decode is memory-bandwidth bound: roughly bandwidth divided by bytes read per token. 45 tok/s sits in the 40-55 band community reports show for quantized ~32B dense models on 1.79 TB/s GDDR7.
Method
The anchor is a June 10, 2026 SemiAnalysis stress test: the firm bought each OpenAI and Anthropic subscription tier, ran long-horizon coding and agent tasks until weekly limits were exhausted, and valued the consumed tokens at public API rates. A maxed ChatGPT Pro 20x seat reached about $14,000 of API-equivalent usage (70 times its price), and Claude Max 20x reached about $8,000 (40 times). The calculator defaults to the more conservative 40 times; the subsidy knob covers 10 to 100 times.
The subsidy value converts to tokens at the selected GPT-5.6 Sol rates with the chosen input-to-output mix and cache-hit rate. Every other path then prices that same token volume. Hardware and rental paths convert the month’s output tokens into an aggregate decode rate over the selected duty cycle, and size a fleet of whole units against each profile’s single-stream decode figure.
Owning hardware costs depreciation plus electricity. Depreciation is straight-line: the purchase price, less the resale-value knob’s residual (default 0%), spreads evenly over the useful-life knob’s months. Electricity multiplies each unit’s rated power draw by the duty-cycle hours and the electricity knob’s rate. The rate defaults to the EIA United States residential average and adjusts from 1¢ to 60¢ per kWh, a band that covers residential grid rates worldwide: GlobalPetrolPrices household averages for 2023 through Q2 2026 run from under 1¢ in subsidized markets (Iran, Ethiopia) to about 47¢ in Bermuda, and Hawaii’s June 2026 average is 52.72¢ (checked September 10, 2026). Use the presets or your utility bill’s energy rate to set a local figure.
Sources
- OpenAI API pricing: GPT-5.6 Sol at $4 input / $0.4 cached input / $20 output per 1M tokens, promotional through at least November 21, 2026. Retrieved September 28, 2026. List fallback $5 / $0.5 / $30 documented August 21, 2026.
- ChatGPT pricing: ChatGPT Pro 20x at $200 a month, as of September 10, 2026.
- DeepSeek API pricing: DeepSeek-V4.1-Flash (model id
deepseek-flash) at $0.003 cache hit / $0.15 cache miss / $0.6 output per 1M tokens off-peak, double at peak. Peak hours are Monday through Friday, 01:00-04:00 and 06:00-10:00 UTC. Retrieved September 28, 2026. - EIA Electric Power Monthly, Table 5.6.A: United States residential average of 18.31 cents per kWh for July 2026. Retrieved September 28, 2026.
- Québec hydro electricity preset: 8.1 cents per kWh. Hydro-Québec Rate D second-tier energy price, 11.142¢ CAD effective April 1, 2026, at 0.724 USD/CAD on September 10, 2026. Checked September 10, 2026.
- Germany electricity preset: 40.6 cents per kWh. GlobalPetrolPrices residential electricity average for Germany, 2023 through Q2 2026. Checked September 10, 2026.
- Hawaii electricity preset: 52.72 cents per kWh. EIA Electric Power Monthly, Table 5.6.A, Hawaii residential average for June 2026. Checked September 10, 2026.
- Vast.ai marketplace: Median hourly ask of the cheapest verified single-GPU on-demand offers (up to 20 per SKU) on the Vast.ai marketplace at retrieval time. Retrieved September 28, 2026.
- TechSpot US retail price tracking (via TweakTown): NVIDIA GeForce RTX 5090 at $4,900 (street price), as of September 1, 2026.
- Get PC Parts eBay sold-listing tracking: NVIDIA GeForce RTX 4090 at $2,400 (used market), as of September 5, 2026.
- NVIDIA DGX Spark price change announcement: NVIDIA DGX Spark at $4,699 (MSRP), as of February 23, 2026.
- Throughput profiles: LMSYS DGX Spark review (October 13, 2025), LMSYS GPT-OSS on DGX Spark (November 3, 2025), and a memory-bandwidth decode method for figures no published benchmark covers. Each profile is labeled measured, published band, or bandwidth estimate.
- TechSpot coverage of the SemiAnalysis findings, alongside the primary thread. Method last verified September 10, 2026: No public re-run of the June 2026 stress test was found as of the verification date; later reporting indicates OpenAI tightened Pro usage limits, so the published ceiling may no longer be reachable.
Assumptions and limits
- Open-weight models on the hardware and rental paths are not GPT-5.6 Sol. The comparison holds token volume constant, not capability.
- The SemiAnalysis figures are API-retail equivalents, not OpenAI’s serving costs. OpenAI does not lose the full sticker gap on a maxed seat.
- Fleet sizing counts decode only. Prefill (input processing) is excluded, which flatters the local paths on input-heavy mixes.
- Throughput profiles are single-stream, order-of-magnitude figures. Batched serving raises aggregate throughput well beyond them.
- Depreciation assumes no residual value unless the resale-value knob sets one, and ignores financing, taxes, and disposal costs. Used-GPU prices vary too much to promise a recovery.
- Electricity assumes grid supply at one flat residential rate. There is no on-site solar or other self-generation, no time-of-use optimization, and no cooling overhead beyond the GPUs’ rated draw.
- Home hardware costs exclude the host system, cooling, networking, and failures; rental costs exclude storage, egress, and interruptions.
- Multi-agent workflows multiply token volume. The Ultra knob scales the implied volume up to 10 times.
API rates, electricity, and rental prices come from a checked snapshot with a guarded automated refresh (bun run calculator:refresh). Hardware prices and the subsidy anchor change only through reviewed edits with dated citations.