alternators used to be very expensive. prices have come down quite a bit over the last ten years. Some still cost a lot, like Stinger, Wrangler, Ohio Gnerator.. but a lot of those are for show cars, too. If you just want it to function and don't care about the "pretty factor" then you should be fine.
Just be wary of the $150 specials on eBay. Most of those are just a cheap rewind job.
Yea, watch out for those "rebuilt" ones... crap. Same kinda thing you'd get at one of those local shops that are all over that claim to make a stock alt do 200 amps for a cheap price.
I've installed quite a few DB alts. As i said not a single failure years later. High rpm output seems good, idle output is about stock, but high idle output is hard to do on a lot of vehicles as you would usually need a physically larger case alt.
my rebuilt alt from mcr is definitely more powerful than stock but i cant grantee it does the rated 200 amps and 130 at idle. only cost me $300 shipped with a lifetime warranty.