Prices really aren't bad if you go MVS, and Vogatek superguns were only like $40-50, iirc. Gotta wait on mine until after the holidays, but hopefully soon!
Samurai Spirits II, IMO honestly one of the best beat 'em ups ever, can be had CIB for AES for about £20. Yes, some games are £500+, but not all - and not all the good ones either. MVS is still the better option (I'd never be able to afford Blazing Star on AES, but I've had the MVS cart for a good while now), but a decent AES collection isn't impossible.As for superguns, etc - please take a look at the blog post I mentioned earlier in this topic ^^~ http://shinjuforest.blogspot.co.uk/2013/04/demystifying-arcade-hardware.html
There's one important thing you missed there - an MVS motherboard for the MVS carts to go into! But other than that you're right