Secret Hills Ranch were recently selling adult birds for $50 each. I think it depends a lot on the quality of the bird. Regular sexlinks are currently selling for $25 at my local feed store.
Remember blue eggs do not candle quite as well so be really sure before you throw. I have had eggs that look like a blood ring in the early stages especially in colored eggs.
This is a great project. I too want to purchase in early spring. Can you tell us what number your egg color is at now? I think that is the hardest part of this project. Or the logest part!
Sounds like you are thinking of cream legbars (crested and uncrested) which are an auto-sexing breed so you can tell as soon as they hatch. The males have a dark dot on their head and the females have a chipmunk like stripe.