Depends on what you are looking for. You won't get that Eterna 1958 KonTiki or any Sinn for $250. If you want a durable, high quality beater with a tiny bit of bling, you can have a Seiko SKX007J type dive watch (J=made in japan vs elsewhere) off of ebay. Look for a "Seiko super oyster II" to upgrade the bracelet to a screw link version with solid ends. Just make sure you go with a reputable dealer with lots of positive feedback.http://cgi.ebay.com/Seiko-Automatic-...item53e0f6c861http://cgi.ebay.com/SEIKO-Super-Oyst...item19bbcc67ea
Those Orient divers are nice also.
IMHO, you should stay away from any brands that you only see on Overstock, Ashford, etc. like Swiss Legend, Haurex, Jules Jurgensen etc. Mostly cheapo stuff. One exception would be Accutron. I have seen some great deals on Shnoop.com for a very nice Accutron diver. There was even a Valljoux 7750 Chronograph for under $400. Quite the steal!! Also be careful buying "vintage" on ebay. You may not get what you pay for.
Another source, if you want to take the time, would be to look at the sales/trade forums of the following web forums:http://www.timezone.comhttp://www.pmwf.comhttp://www.watchuseek.com
I have been buying, selling and trading off of all of these forums for years and haven't been burned yet. There are some great deals on some nice watches and the fact that you are dealing with hobyists makes it rather safe. Good luck!!