What the hell is going on with shops?

as the owner of a shop ( boat repair ) there is nothing that irritates me more than a customer showing up at my shop having already diagnosed problem with part in his hand asking " how much to put this in ? " I have givin crazy prices to get rid of them . The reason is because if their diagnosis is wrong or part fails ? who is customer gonna come snivel at ? me . I am not taking the side of the shop you went to because that price was ludicris . I am just saying ...... You dont bring your own steak to a resturaunt and ask them how much to cook medium rare .