>additionally, for virtually all stores on instacart.com now, we are simply passing on the pricing that the retailer has given us (which may or not be marked up from their internal prices -- but we do not control)

IC is responsible for signing the contracts they have with retailers, IC is also the most visible partner for the end-user. As you can see from this thread, attempts to kick the blame down(up?) the supply chain will only fall on deaf ears.