Good question. Certainly a surface "blemish" perhaps can be treated like any other piece of sheet metal and pulled out, painted, etc. But what if the damage is more substantial? I bet most body shops haven't seen the likes of a smart tridion!
BTW, the $1850 estimate involves much more then just replacing the fender. Looking at the original photos, I assume the tail light could have been damage, and looks like issues with the wheel well as well. So, $1850 may be what it takes to be "as good as new".