I have had a couple trigger issues from fooling with them too much, and was looking at some options. I called Carver about one of the trigger kits he builds, and he said there is a big difference between the Glock 3.5/4.5 and the other connectors. He said that at times others are requested, but it takes considerably longer to get them working as well as the Glock. He sells all of them, but reccomends the Glock by far. Everyone charges more for it, I don't think any place in particular is trying to gouge on it, except possibly Glock.
I bought the cheap ones before, but one started galling from lack of lube, and one had the wrong angle and lost tension when I changed it a bit, and now won't hardly let the bar grab the striker. I think I will go factory next time around and see if it makes things easier. Paying $10 more could be cheap if it isn't a constant hassle.