$9.60 for 1,000 Price Checks: A Build Budget

01 / A $9.60 operating receipt, not a pricing promise

A useful price-comparison assistant should answer one question: which matching offer has the lowest payable total? Building a chatbot is the easy part. Collecting reliable prices, accounting for delivery, and refusing misleading comparisons take more care.

Start with a budget for 1,000 completed comparisons per month. The numbers below are illustrative planning assumptions, not quoted CheapRelay rates or measured production results. Replace them with your selected model’s current rates and your data supplier’s actual charges before spending money.

• ■ Input: 1,000 requests × 2,000 tokens = 2 million tokens. At an assumed $0.50 per million: $1.00.
• ■ Output: 1,000 responses × 300 tokens = 300,000 tokens. At an assumed $2.00 per million: $0.60.
• ■ Product-data access: an assumed $5.00 allocation for 1,000 comparisons.
• ■ Hosting and storage: an assumed $3.00 monthly allocation.
• ■ Total operating budget: $9.60, or $0.0096 per completed comparison.

This excludes development time, payment-processing fees, and any paid monitoring. The $5 data allowance is especially uncertain: licensed feeds or frequent live lookups can make acquisition cost much larger than inference cost.

02 / Make the assistant compare $45.34 with $45.90

Consider two hypothetical offers for the same product, condition, and package size. Assume both sellers apply 8% tax to the discounted item price plus delivery. Real tax rules vary by jurisdiction, so production calculations need location-aware inputs.

• ■ Store A: item $39.99 + delivery $5.99 − eligible coupon $4.00 = $41.98 before tax.
• ■ Store A: tax $3.36, rounded to cents; payable total $45.34.
• ■ Store B: item $42.50 + delivery $0.00 = $42.50 before tax.
• ■ Store B: tax $3.40; payable total $45.90.
• ■ Result: Store A is cheaper by $0.56, provided the coupon applies.

Without that coupon, Store A costs $49.66 under the same assumptions. Store B then wins by $3.76. Coupon eligibility is therefore a required field, not decorative text. If eligibility is unknown, show both scenarios instead of declaring a definite winner.

03 / Keep arithmetic outside the language model

Use a small pipeline: retrieve offers, normalize fields, calculate totals, then ask the model to explain the result. Store the product identifier, variant, condition, quantity, currency, stock status, shipping charge, coupon restrictions, source address, and retrieval time.

Perform money calculations in integer cents or a decimal library. Let application code rank valid offers. The model can interpret a shopper’s request and explain exclusions, but it should not invent delivery charges, infer missing taxes, or silently substitute a different pack size.

Missing shipping should produce “total incomplete,” not “free shipping.” A listing with no verified stock should not beat an available offer merely because its displayed price is lower. Keep merchant text separate from instructions: product pages are untrusted input.

04 / Route compact requests through one API key

CheapRelay fits at the explanation step: it provides pay-as-you-go AI access through one key, with OpenAI-compatible routes under https://api.cheapapirelay.com/v1. An existing OpenAI SDK integration can use that base URL and a supported model identifier.

There is no monthly fee or subscription. Billing follows real token usage, including cache reads and writes, so cached traffic still belongs in your ledger. Check current pricing rather than treating the illustrative rates above as an offer. Sign up for CheapRelay when you are ready to test this workflow with a small, capped budget.

05 / Audit the receipt after the first 100 comparisons

Record input tokens, output tokens, cache charges, lookup charges, retries, and completed comparisons. Divide actual spend by completed comparisons, not API calls: failed requests and repeated lookups still cost money.

Review mismatched products and stale prices separately from writing quality. Before scaling, test coupon exclusions, unavailable stock, different currencies, and missing delivery fees. A defensible assistant returns a timestamped receipt with explicit uncertainty. A fluent answer without a trustworthy total is just another shopping expense.