I was thinking about a related idea recently - how much is my grocery information privacy worth for me? Summed up, I'm currently saving just over 11% on all the groceries + ~7% on fuel cost by sharing that information with 5 companies. (car insurance, CC, shop card, honey, airline) I'm not attached to this, I'd rather the programs like this get destroyed. But also by stacking the offers, I believe I'm getting more va…
I don't think this is the exchange you are making, though.
The money you save here is no different from couponing: it's a way for retailers to price differentiate and charge the other customers more.
You are being charged a fairer price (still profitable for the retailer), for actively paying attention to what's cheaper; that'll be unrelated to the price or value of your data.