Depends. Most of the merchant decides. However for "premium" brands the manufacture sets the price and won't let you go below it.

Weber grills rarely go on sale or clearance because you need permission to do so. Menards near me often has 11% rebate on everything sales - they do not sell Weber grills. Home Depot matches Menards 11% rebate on everything, except things Weber grills where they are not allowed to discount.

I know of one case where a golf store threw in a free hat with the full price purchase of an expensive putter. The customer was an undercover agent for the putter company and the store no longer got more product from that company.

I know there are a lot more examples, but I don't know them.