Best i could get from my reading is that the premium worked in the same way, but with a wider selection of items and possible some higher discounts. I think the free version is much more than just coupons though that's at least part of it. There appear to be some substantial direct...
Best as I can find out is they use several methods.
They do sell advertising, they do use/sell at least some or your data they collect on you to 3rd parties -- how much and exactly what is harder to say.
A lot of the savings they get you are by joining/attaching to multiple large groups (PBM)...