That's a really good price for pure Ameracuanas. If you want cheap, you should go with the "Easter Eggers" that commercial hatcheries sell. They aren't show quality and won't breed true, but they will lay a lot of pretty eggs. It really depends on what you want them for. If quality matters, pay the going price. When you think about it, you're going to have a lot more than $100 invested in housing, feed, and other care items. IMO, the initial acquisition cost of poultry is a bargain.
It's sort of like having kids. Getting them is pretty cheap and easy, at least compared to the total outlay of time, money and exasperation.
Personally, I'd recommend buying the $6 chicks if you are serious. Their eggs and chicks will be more valuable to others also, and you can make back a lot of the additional costs. Note, I'm not saying you will make an overall profit, that is another thing entirely, but the difference in the initial cost can pay itself back easily.