I've purchased plants that were really nice from bonzaibob and eastfork (both ebay vendors) for a good price. Really can't complain about herter either.

Eastfork is great, why not use their website though?

I'd avoid auction items. People on ebay get really carried away and overpay. A few months ago I bid about 30 dollars for a 3 or 4 year old dwarf japanese maple, an obscure variety, that ultimately sold for 140 bucks or something like that. I wonder if whoever won that item feels like it was a good value (if you bought that "Vic's Broom" please stand up). Even if its rare, Id much rather substitute another similar variety thats widely available for much much less money. Some people are so extravagant.

If buying on ebay Id go with the fixed price items. and also I dont like to buy freshly grafted maples in band pots. Usually not a good value.