Asked them how much to put a vesa stand on mine whilst it was in for repair. Quoted me £125 so it can be done. Not sure of price swopping vesa to stand though

Mine is in the Apple store to have the logic board replaced as the imac won't boot up. I guess if one thing like ram or storage goes down the whole lot needs changing. 2 port logic boards are £310 plus £85 labour to swop out.