The price tag is only the first sentence of the deal

A listing shows $19.95. A buyer assumes that is the amount needed to obtain the item. The seller means $19.95 per pack before a regional surcharge, delivery and tax. A wholesaler means the same number but only after a minimum order of thirty packs. The screens display an identical figure while describing materially different transactions.

Price is not a scalar waiting to be formatted. It is an offer or observation whose meaning depends on the unit, currency, product, seller, time and conditions.

A dollar sign is used by more than one currency. Decimal separators and currency display conventions vary across locales. The Unicode CLDR data^{[1]Unicode CLDR data} helps applications format monetary values, but formatting cannot determine which currency or contract an ambiguous price intended.

A robust amount needs an explicit currency code and amount representation. It also needs a rule for rounding and precision, especially when accounting, discounts, tax and display values differ. Binary floating-point is a poor default for exact decimal amounts; using integer minor units or an exact decimal type is an engineering choice that must match the currency and the operation.

Suppose a retailer offers a unit for $20, freight costs $40 per order, and the minimum order is twenty. A naive storefront compares $20 with a competitor's $24 and declares victory. At the minimum quantity, the first supplier's landed pre-tax cost per unit is ($20 × 20 + $40) / 20 = $22. If the comparison is for one unit delivered today, the first offer may not be purchasable at all.

Now add returned goods, lead time and quantity breaks. A useful comparison must state the scenario rather than pretending to produce a universal cheapest seller.

A scraped price may be historical, restricted to certain customers or already withdrawn. Even a current public price may not constitute permission for an agent to purchase. A system should distinguish an observed listing, a current confirmed quote, a customer-specific offer, and an authorized order.

That is the missing boundary in many attractive AI-shopping demos: a plausible number is promoted into purchasing authority. A real transaction needs a lawful seller relationship, accurate terms, a buyer's consent and verifiable settlement.

Preserve amount, currency, unit of measure, quantity tier, tax inclusion, fulfillment conditions, vendor, applicable region, effective period, evidence source, and confidence in current availability. Compare only like-for-like offers, with calculations visible enough to challenge.

This is why the Aurekai catalogue and room-planning example separates observed product prices from scenario costs. A room plan can reason over material prices without manufacturing the right to buy.

The price tag matters. But the deal lives in the qualifications, and a system that hides them cannot help a customer make an informed choice.