I'm just sayin', I've seen fake boobs before and I've seen real ones. That character you linked is drawn like she has implants, so if hers are fake, I dunno how "real" yours need to look.
If you have any friends who owe you favors and who know how to sculpt and cast, you might be able to get them to help you (or commission them) to make a similar prosthetic for less than one of those, and it'd be custom fit to your body. If you've seen the show Face-Off at all, it'd be similar to that.
Also they have stuff on ebay that's less expensive ($259 is still pretty expensive but it's better than $500).