They do charge quite a bit but I've actually seen yorkie mix dogs for more than that.
For some reason cross breeds have been in demand now since you are gettin 2 breeds in one ( I guess). There is a organization now that recognizes some of these breeds and they cld be registered. Sire and Dam must each be purebreed of whatever particular breeds is gonna be used. I believe its the american canine hybrid club.
I plan on breeding my bichon frise with my yorkshire when the time is right. Which is now called a Yochon.
Heres a site I found of some..if u scroll all the way to the bottom you'll see some pics..
http://www.rollingmeadowspuppies.com/YoChonPage.html
Heres a pic of one..