The one thing I usually consider is that it isn't usually a .99 delivered price on eBay.
If you're lucky you end up paying around $2.00-$3.00 to have it delivered so the total cost ends up being $2.99-$3.99 delivered per card. Of course, if you get multiple cards from a seller they usually give you a break.
I'm not saying I love the COMC shipping price, but I do take the cost of delivery into consideration when I buy.
COMC 20% Auto Accept - Bulk Discounts Arranged - Low Prices!