Go to
www.teehed.com! I don't know about their pricing, but it's an awesome site for ideas on recruitment and bid day shirts. They have a breakdown of pricing for different quantities, but you can always print out the idea and see if you can get it cheaper somewhere else. I found great shirt ideas there, which turned out so cool! We had one of the designs done on shirts at another place locally, and we only paid like $8 a shirt!
Good luck
p.s. My favorite bid day shirt is: it's not what you've just become
it's what you've always been. It has this great daisy flower on it and it's gorgeous! Another cute one is this one with a little girl throwing a penny in a well and says "wishes do come true!"