# Model switch cost calculator > Compare two models against your own token mix, with the crossover ratio where they tie. Exact decimal arithmetic, so the totals hold up. URL: https://getculpa.com/model-switch-cost-calculator Last reviewed: 2026-08-02 ## Answer This model switch cost calculator prices two models against the same token volumes and reports which one your own mix favours, plus the output-to-input ratio where the two tie. Culpa, a local-first LLM cost, margin, and forecast ledger, computes both totals in exact decimal, so a migration gets decided on arithmetic rather than on a headline rate. ## Why this happens A migration usually gets argued on one number, the input rate, because that's the column a shortlist has room for. Two models with different spreads between their input and output rates cross somewhere, and which side you sit on is decided by your own output-to-input ratio rather than by either rate card. Some pairs never cross at all, where one model is cheaper on both rates and the answer holds whatever your mix. Knowing which of those two situations you're in takes half a minute, and it decides whether the choice needs a meeting. ## What this usually looks like - A migration is being argued from input rates alone. - Nobody has stated your output-to-input ratio for the workload in question. - The saving was estimated once and never priced against real volumes. - Two features with very different shapes are assumed to move together. ## Common mistakes - Deciding a switch on the input rate. Why it hurts: The dearer output rate can reverse the answer well inside normal workloads. Do instead: Price both models at your real volumes. The totals settle it in one step. - Assuming every pair of models has a crossover. Why it hurts: Plenty of pairs never cross, and hunting for a switch point wastes the analysis. Do instead: Check whether one model is cheaper on both rates. If so, your mix changes nothing. - Migrating a whole product on one comparison. Why it hurts: Features sit at different ratios, so a single answer can be right and wrong at once. Do instead: Run the comparison per feature and let each land where its own arithmetic puts it. ## Self-check - Pull your uncached input, cached input and output volumes for one feature. - Price your current model and the candidate against them above. - Read the crossover the calculator reports and compare it against your own ratio. - If your ratio sits near the crossover, the saving is small and the risk probably outweighs it. - Repeat per feature rather than trusting one account-wide answer. ## The same migration, two features, opposite answers (illustrative) Moving from GPT-5.4 nano at real rates of $0.20 per million input and $1.25 output to Llama 3.3 70B Versatile on Groq at $0.59 and $0.79, both effective 2026-07-02. Volumes are modelled. Crossover: ($0.59 - $0.20) / ($1.25 - $0.79) = 0.85 output tokens per input token Retrieval feature, 200M input and 20M output, a ratio of 0.10 GPT-5.4 nano: (200 x $0.20) + (20 x $1.25) = $40.00 + $25.00 = $65.00 Llama 3.3 70B: (200 x $0.59) + (20 x $0.79) = $118.00 + $15.80 = $133.80 Drafting feature, 40M input and 48M output, a ratio of 1.20 GPT-5.4 nano: (40 x $0.20) + (48 x $1.25) = $8.00 + $60.00 = $68.00 Llama 3.3 70B: (40 x $0.59) + (48 x $0.79) = $23.60 + $37.92 = $61.52 The same migration costs $68.80 more on retrieval and saves $6.48 on drafting. One decision, two features, and the arithmetic disagrees with itself unless somebody runs it twice. ## Cost figures Every figure carries its confidence and its source. No figure on this site is provider-reported. - 0.85 — output-to-input ratio at which the two teardown models cost the same [calculated] Source: ($0.59 - $0.20) divided by ($1.25 - $0.79), using real GPT-5.4 nano and Groq Llama 3.3 70B Versatile rates per million from the price book, effective 2026-07-02. - $61.52 to $133.80 — modelled monthly cost across two features and two models, cheapest to dearest [estimated] Source: The four totals in the teardown arithmetic at real rates. A range because the token volumes are modelled. ## FAQ Q: What does the crossover ratio mean? A: It's the output-to-input ratio at which two models cost exactly the same. Below it the model with the cheaper input rate wins and above it the other one does, so the number tells you which side of the decision your own traffic sits on. Q: What if the calculator says the two never cross? A: Then one model is cheaper on both input and output, and no token mix can change the ranking. That's the easy case, and it means the price question is settled before you start. Q: Should I switch on cost alone? A: Cost is the part arithmetic settles in a minute, which is exactly why it's worth settling first. Quality on your own task needs a sample and someone's judgement, and it deserves the time that closing the price argument frees up. ## Sources - OpenAI API pricing: https://developers.openai.com/api/docs/pricing - Groq pricing: https://groq.com/pricing Run the free Cost Leak Scan: https://app.getculpa.com/scan?source=pseo&slug=model-switch-cost-calculator&cluster=calculator Machine-readable index of every guide: https://getculpa.com/api/pages Human-readable index of every guide: https://getculpa.com/guides Site overview: https://app.getculpa.com/llms.txt Privacy: Culpa runs on your infrastructure. Your prompts and responses never leave it. Culpa counts calls to run your plan, and it fails open, so if it ever breaks your app keeps running.