Q: You set a price with your supplier based on the expected price from your customer. If your customer lowers his price, may you renege on the confirmed price with your supplier or cancel the order and buy the merchandise from him again at a lower price?

A: If the order from the supplier was completed with a kinyan, you cannot renege on the price or cancel the order, unless there was a clear statement that the agreed price was based on the expected price from the customer (C.M. 207:3 and Pischei Teshuva #5). A properly signed order form might be considered a kinyan if the common commercial practice is to consider such an order as final (201:1).

If there was no kinyan, the Rama (204:11) cites two opinions whether there is a moral obligation to uphold a commitment when there was a change in market circumstances meanwhile. The Rama holds that there is, but a number of Achronim question this ruling (Shach 204:8).

In any case, reneging on the price and cancelling the order and re-buying would seem to have the same rule.