Well, as you know there are several sellers on eBay selling business cards at this time and it has become a large market.  Here are a few pointers to help you decide who would be the best choice for your business.

1 - Check out their Feedback.  Not only to see what they have received - BUT (MOST IMPORTANTLY) - Check out each item they seller has received feedback for and the pricing on it.

What we have found is that many of these sellers have a low price to begin with - but it rapidly changes each time they put a new listing out for business cards.  Knowing if you are going to get the SAME PRICE for a CONSISTENT period of time is very important!  You might like the $19 special, but will it really be that price the next time you order - PROBABLY NOT?  Detailed feedback will tell you all of that!

2 - Paper - make sure it is either 14pt or 16pt, anything less is probably flimsy and probably home made.... and anything with UV coating - is the way to go if you like a very high gloss protected card!

3 - Look to see what the seller Buys on eBay (very important) - that will tell you if they are an actual company or just someone trying to pass themselves off as a real printer.  Someone selling or buying toys probably works out of the house and has limited skills and resources to get you what you need!

Here is a great start to help guide you, we will add more later after we research this more....