I guess that depends what your idea of expensive is? I paid around $160 - $180 CAD for mine from
www.thebreastformstore.ca and I've been very happy with them. That is a fair bit of money to some people though, me included. I just wanted them badly enough and had the room on my credit card at the time. Sure I could have shaved a bit off the top of my student loan instead but I think it was worth it

Also, now that I remember my browsing, size matters as far as cost goes. I think my forms are size 8 which was as big as I could get without upping the cost another $20 or so. But that's probably big enough for almost anyone, I'm pretty tall and well built (for the guy I am to the rest of the world) and they suit me nicely.
And as far as
thebreastformstore.ca goes they ship their parcels discretely so I didn't have to worry about any embarassment.