[villagetinker]

OP, sorry to hear about the problem. This was probably a misunderstanding, we did have something similar, but it was so minor that we let it slide. No idea if you have a block or stick house, but I am guessing in any case it was framed for the smaller window, and that is why the high cost to change. IMHO, let it go for now, and have it changed later, I am GUESSING it will be lower cost, but you will have to deal with the dust, etc.

Actually, depending on the house, I am surprised they allowed that change. On our house if there was a fire in the closets or master bedroom the ONLY EXIT from the master bathroom is that small window.....while I KNOW these windows are NOT designated emergency exits, I still like having a window I can open and get out just in case.