No one does that, usually broken necks get glued anyway. Getting a new replacement neck is hard to find and if you do, in most cases it'll cost you more than glueing or buying a new guitar alltogether. It is however better to buy a bolt on if you ever think about taking it all apart and go DIY on it. Like some dudes and me on this forum. Throw away the Ibanez RG body and buy a body black on the internet.
Imo you should start thinking about this dilemma when you are going to get a custom.
It depends.
Anything Fender compatible you can get a neck for <$100 fairly regularly. Ibanez is maybe a bit more depending on how picky you are (whole used guitars are as cheap as $200, even MIJ). Even Jackson and ESP/LTD isn't too terribly hard to source in the world of forums and gear trading site.
You throw your old hardware and nut on the new neck and you're ready to go. You'd be surprised how popular of an option that is.
It's only in the ERG world that neck swapping is as extremely uncommon.