The price adjustments due to coupons, rewards programs, and food stamps are all publicly available (transparent). No hidden algorthms. If the coupon says 10% off, then that's what you get. It's not maybe 10% off or maybe something else depending on a secret recipe like if the temperature is between x and y and you have a name that rhymes with Pobert or whatever else some AI has figured out.

The opacity is that people who don't have coupons generally don't know they exist. Coupons are a kind of price discrimination assuming that people with less time to coupon-hunt are willing to pay more.

The coupons I get in the mail from Fred Meyer (a local Kroger subsidiary) are custom, printed for me based on my purchase history. I can’t guarantee they alter the discount for the same item based on the customer, but it seems logical.

Also, the coupons they print on the fly with the receipt could be custom priced for that specific customer, as well.

Sometimes I receive a coupon in the mail but my sister who has the same last name as me and lives in the same town does not. Whatever algorithm causes that is pretty opaque.

Or their friend is the cashier and gives them the staff discount, or the cashier is crooked and over charges the person, or the person steals it.

Prices are different in different physical neighborhoods. Why shouldn't it be the same for digital neighborhoods and the user has an iPhone, or extra cash lying around? It offends your (and my) puritanical sensibilities, but prices are all made up and have no relation to what something costs to make (it's true. think about that deeply) anyway, so of evils in the world, Uber's pricing strategy is hardly the worst of it.