When asking a dealer who sells a lot of glocks, why he didn't have more with night sights, he responded, "people have a price in their head with Glocks" , if have to charge them another 100 for the sights and $25.00 to install them, they will usually not want them, you went from a 500 to a 625 dollar gun, and that 22% hike will turn them off. If he continues I was selling them a $1000.00 pistol, it would make very little difference.
Fact is folks have price points, in their heads, and a dealer and I said at the same time , this passed weekend, "it doesn't matter what I put in it, it doesn't change what your going to pay me for it. Just because I spent a day of my time polishing parts and changed a trigger shortened up the pull and removed the slop, two dealers would not even take a look at the gun once they found out they were modified.
The guy who had 1911's was trying to convince me that every 1911 he buys must be restored to it's original mim parts, or his liability insurance won't cover him.
So all those wilson beavertails triggers hammers and springs, you are tearing out I asked?, yep he said I have to. I quicklly walked away and sold the gun 10 feet away for more money. There is no end to the garbage you will hear at a gun show.
The good thing with Glocks is you can return them to stock pretty fast, unless you started cutting things off. After 6 of them I never touch them other than to put a front NS on, and a plug in the hole in the grip. They really don't require any custom work, same with M&P's.