I've bought a few vintage Russian watches from sellers on eBay over the last month or so, just because the styling is funky and they're really cheap. My buys have been in the £30 range, and for that money I'm happy with something that looks cool/old even if it's not strictly accurate. I very much doubt the cheap ones are really "vintage" - or if they are, they're cobbled together from mismatched old and new bits. It's like everything online - if it's truly vintage, it's rarer and costs more... and it gets copied a lot!
So, my experience has been fine because I just made a "best offer" on the watches I fancy the look of and got them cheap (because they were cheap to start with). I'm not even bothered that the crown dropped off the first one within 10 minutes of owning it, while I messed around trying to work out how the heck you set the date on a Poljot...
BTW, I've started following the Russian watch collector section on WatchUSeek since getting interested - there's a TON of useful information there about the watches and the various online dealers.