Aside from the subscription model involved, this is identical to (but with a better producer margin at 70%) what Handango and other PalmOS app distributors offered.

I remember developers being up in arms because (a) Handango wanted a 60% cut, (b) you had to offer the same pricing on the Handango store as anywhere else, and (c) you couldn't direct people out of the Handango store.

The clause you're talking about is pretty standard in reseller contracts everywhere. I wouldn't be surprised if there were one in the distributor contract for selling software in boxes at Apple stores, where the manufacturer makes 10% or less of the retail price. Also, Amazon has to make certain deep discount prices only visible after clicking or putting into the customer's cart because while they can sell for less than the MSRP, they aren't allowed to advertise (or let searches advertise) at that deep discount price.

Edit: Added (c) as I remembered it while rereading this.