Cheap vs Expensive AI Model
The same prompt sent to a $0.14 model and a $30 model. Three real-world scenarios with May 2026 pricing. The point of this page is not to tell you "always pick cheap" — it is to show you when each tier is the right call.
Prompt
"Classify this support ticket into one of: billing, bug, feature-request, account, other. Reply with the single category."
600 input + 12 output tokens × 250,000 requests/month
Cheaper
DeepSeek V4 Flash
$0.14/1M in · $0.28/1M out · 78/100 quality
Per call
$0.000087
Per month
$21.84
Premium
GPT-5.5 Pro
$30/1M in · $180/1M out · 95/100 quality
Per call
$0.0202
Per month
$5,040
Spread: 231x. Annual delta if you used the premium model for everything: $60,218. A bread-and-butter classification job. The "expensive" tier offers no measurable accuracy lift on this kind of task in our internal evals.
Quality note: On a held-out 5K-ticket eval set, both models produced the same label 99.1% of the time. Cheap wins by an enormous margin.
Prompt
"Draft a 4-paragraph email response to a customer who is unhappy with our refund policy. Tone: warm, firm, brand-aligned."
1,500 input + 350 output tokens × 80,000 requests/month
Cheaper
DeepSeek V4 Pro
$1.74/1M in · $3.48/1M out · 88/100 quality
Per call
$0.0038
Per month
$306
Premium
Claude Opus 4.7
$5/1M in · $25/1M out · 93/100 quality
Per call
$0.0163
Per month
$1,300
Spread: 4x. Annual delta if you used the premium model for everything: $11,925. Mid-complexity drafting. Tone fidelity matters; users notice quality differences here, but a mid-tier model usually carries the load.
Quality note: Side-by-side blind reviews favoured Claude Opus 4.7 in 58% of cases — clearly better tone, but both were judged "ship-ready" 95%+ of the time. The cheaper option is the right default with the expensive one as a quality-bar override.
Prompt
"Given this 8K-token contract, identify all clauses that conflict with our standard MSA and explain each conflict."
9,000 input + 1,400 output tokens × 800 requests/month
Cheaper
DeepSeek V4 Pro
$1.74/1M in · $3.48/1M out · 88/100 quality
Per call
$0.0205
Per month
$16.43
Premium
GPT-5.5 Pro
$30/1M in · $180/1M out · 95/100 quality
Per call
$0.5220
Per month
$418
Spread: 25x. Annual delta if you used the premium model for everything: $4,814. High-stakes reasoning where a single missed clause has a real cost. The expensive tier earns its premium here.
Quality note: On a 50-contract gold-set, GPT-5.5 Pro caught 94% of the conflicts. DeepSeek V4 Pro caught 77%. The 17pp gap on a high-stakes legal workflow justifies the price.
The decision rule that actually works
For any given prompt class, ask three questions: (1) Can a cheap model produce the answer with acceptable accuracy on a 200- sample held-out eval? If yes, the cheap model wins, full stop. (2) If no, can a mid-tier model do it? Same logic. (3) If still no, what is the cost of being wrong on this prompt class, and is it bigger than the price gap? Only when the answer is yes does the premium model justify itself.
Most teams skip step 1 and step 2. They use the premium model everywhere, then are shocked when the bill arrives. Step 1 is free engineering effort that returns 50-95% of your monthly LLM spend. Step 2 catches the residual cases. Step 3 is the right place to spend money.
Related
- AI Token Cost Calculator — three scenarios across all 25+ models
- Model-Mixing Cost Savings — what cascade routing saves on real traffic
- Mixture-of-Routers (technical deep-dive)
- AI Model Leaderboard
All prices from official provider pages and OpenRouter as of 2026-05-06. Quality notes are from internal Swfte evals against held-out samples; methodology is described in our LLM routing writeup.