Okay, but don't overlook just going in and asking. You take a clean frame with nothing on it but the old crank and they might just remove it for nothing. YMMV.
I used to think shops charged an arm and a leg too. However to my surprise, when I did get them to do stuff for me, I always felt they didn't charge enough. And many times, just going into shops and chatting with the mechanics or shop owners when it wasn't busy would get me free stuff. Something they may have just taken off and the bicycle owner didn't want back.
But that was prior to the current situation.