Commerce Offer

Provides a store entity, a store reference field, and an offer entity.
Offers provide a way for each store to have different prices for a product. One store can have multiple offers (prices) for the same product.
The original price field on the product is hidden.
A rule is provided that replaces the product price with the lowest offer price from the selected store.
Right now the only way to set a current store is by calling commerce_offer_set_current_store(), which drastically reduces the module's usefulness.

Could be used as a basis for a real marketplace module.