It wasn't on a firearm, but Cheaper Than Dirt marked up MagPul 30 rounders to something like $40 after the election. If that wasn't bad enough, they claimed (lied) the MSRP was like $50, so you would still "SAVE 20%!!"
I don't shop there now.
edit: Here it is. I was wrong - they claimed "List Price" was $60 so they could still claim you were saving.