Refresh copy for 4M SKUs

Context

A retailer regenerates product copy for ~4M SKUs each season. Every call carries a large, identical brand voice + policy prompt; caching that shared prefix collapses the input token bill.

The decision

Caching is the build versus buy lever, with a high shared prefix cache share the per call cost drops enough to make the feature economically obvious.

What most miss

Teams price this at the naive per call rate and conclude it's too expensive. The brand prompt is most of the tokens, cache it and the economics flip.

Stakes

Priced without caching, a 4M SKU refresh looks unaffordable and the feature dies in the business case.