If the conversions were actually sold for cheap, then all would be good.
In a way, they are cheap believe it or not. There is a sac cart which is of course a JP Fatal Fury 3 most of the time, so there goes $30-$60 depending if the cart is loose and/or good condition. Then you have the original MVS cart of said game, which in most cases are $60 carts. Then you have the labor of de-soldering chips from both carts, soldering the chips onto the home cart, then changing the jumper connections. Total cost of a fresh conversion cart with just insert and cart sticker done to it = $180-$200. So you are paying roughly $60-90 for the labor, which is somewhat fair considering all the annoying solder work.
Any already owned and used conversion cart should go for $140, which they sometimes do. I got my Shock Troopers 1 conversion from cgame on Ebay who is from Taiwan about 5 years ago. He does great work and charges $180. I think he stopped doing conversions around 2 years ago. I still think conversions should not be any more than $150 really.
Still, you can go the MVS converter route or just get/build a CMVS. The looks game and console wise are rough as hell, but you still get to play the games on original hardware. If you think paying $400-$500 for a CMVS is too expensive then that is kinda silly. Think about what most games will cost on the AES home cart format in the long run. You still save going with MVS. Using the newest and best converter can be tricky, as some AES home consoles have zooming glitches with games.
I still want a MVS cab, but they don't really have them ANYWHERE in the f*cking south. Man, this area has nothing to offer when it comes to old school gaming. I always like AES collecting and all but only within a somewhat reasonable pace. I pretty much have all the games I want for it, minus Metal Slug 1, 2 X, Shocktroopers 2nd Squad, Pulstar, Blazing Star, and a few bit more. That is just due to ridiculous prices. Other than that I have all the 1 on 1 fighters I want, so I am happy. Eventually I will get a MVS cab if I find one, or just say to hell with it an make a CMVS.