I have bought a few (and sold a few) and bought all but one from eBay. The other one was bought on shopGoodwill.com. I haven't paid more than $220 for any of mine, but I also don't want or need one that is pristine. I buy them to use them. It is a bit of a risk, not being able to try it out, but I've been lucky, I guess. My advice is to keep an eye on Craigslist, if there is one in your area, because I've sold a couple of mine there and always end up selling it for less than I paid for it. You can sometimes get lucky on the Goodwill site -- I bought one there for $101 that "didn't work" and it just had a thread jam that I cleared in three minutes. And there are occasional bargains on eBay. I just set up a search that has a price limit on it, sort it by "ending soonest" and keep an eye on the ones I might want with the watch list.
Oh -- make sure the machine you buy has its bobbin case, preferably an original (some of the reproductions don't fit quite right).
Good luck! They really are fun machines to sew with.
ila