How to Use LLM Vendor Lock-In Cost
The LLM Vendor Lock-In Cost calculator estimates engineering hours from prompt complexity and eval suite size, applies your engineer hourly rate, adds downtime opportunity cost, and computes payback if the new vendor offers a discount.
Bottom Line
This calculator translates prompt rewrite effort, eval suite size, downtime, and engineer cost into a single switching-cost dollar figure with a payback window.
LLM Vendor Lock-In Cost
Engineering, downtime, and payback when migrating between LLM providers.
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What It Does
Use the calculator with intent
The LLM Vendor Lock-In Cost calculator estimates engineering hours from prompt complexity and eval suite size, applies your engineer hourly rate, adds downtime opportunity cost, and computes payback if the new vendor offers a discount.
AI engineering leads, founders, and procurement teams sizing the cost of moving off OpenAI, Anthropic, or any other LLM provider.
Interpreting Results
Payback months under 12 is typically a green light if you also have technical reasons to switch (latency, capability, support). Higher than 24 months and you usually want to wait for vendor pricing to converge.
Input Steps
Field by field
- 1
Current Monthly LLM Spend
Enter your current LLM bill so downtime opportunity cost has a basis to scale against.
- 2
Prompt Complexity Score
Rate prompt complexity 1 to 10 — the multiplier that turns into prompt-rewrite engineering hours.
- 3
Eval Suite Size
Number of evaluation tests that will need to be re-run or re-calibrated against the new vendor.
- 4
Loaded Engineer Hourly Rate
Loaded engineering rate (wage + benefits + tooling). BLS data pegs senior software engineer loaded cost at $100 to $200/hr in the US.
Use a blended rate if the team mixes seniority levels.
- 5
New Vendor Price Discount
Discount the new vendor offers vs current spend. Drives the payback months calculation.
Common Scenarios
Use realistic starting points
Small-team migration
Current monthly spend
2000
Prompt complexity
4
Eval suite size
30
Total switching cost typically 1 to 3 months of current spend.
Enterprise migration
Current monthly spend
100000
Prompt complexity
10
Eval suite size
800
Engineering hours can dominate downtime cost; check the total payback months.
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Sources & References
- BLS — Software Developer Wages — U.S. Bureau of Labor Statistics
- Stack Overflow Developer Survey — Stack Overflow
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