I asked an online shop I frequent if they have an API, as they discount some inventory sometimes, to which they responded there is no public API. It's easy enough to find (using Inspect->Network->XHR) how they serve data, and with just five minutes of work, their raw JSON can be loaded in Python and polled for specific brands/categories/individual products, including anything flagged for a discount.

Programmatic? Yes. Against their wishes? Also, yes.

The guilt or bad feelings subsided after realizing I'll use more of their bandwidth how I was searching before via the browser. Using the API, I see when the last inventory update occurred, and only after this will I search their discount inventory.

(In any case, if they are on EC2, I cost them 3 to 8 cents per month, estimating high, which they have certainly recouped.)