Most dealers will comply, and have extra ties available. But some don't.
Any dealer (licensed or private sale) that won't remove the zip tie won't sell a gun to me.
I don't mind the ties, but really, someone trying to sell a several hundred dollar gun who won't cut a cheap zip tie? What kind of moron is that?
Providing your own replacement tie for a gun you are NOT going to buy is a nice courtesy, but really not a requirement. After all, today, the ties are part of the price of doing business at a show.