I have paid as low as $25 (shipping included) for 6+ eggs and up to $55 (shipping included) for 8+ eggs. I have seen well known breeders sell 6+ eggs for over a hundred dollars on eggbid.com. The more well known the breeder, the better the stock, the more show wins, etc... the more you can ask. Just from looking so much, I would say you might want to start off on the lower end and as you get more positive feedback, start raising the price. People will pay for good quality or for a breed that is not commonly offered or a color of breed that is rare to find. (For the record I am not specifically speaking of blue wyandottes, but this seems to be the general rule for most breeds, except production lines and crosses, which tend to go for much lower. The better the quality and the more well known the breeder, the higher the price.)
Hope this is helpful.
Hope this is helpful.