Dildo machines occupy a small niche. I've never met any girls who actually owned one. Most masturbating girls will use the regular hand-held dildos. The Sybian saddle (seen on the Howard Stern show) is not cheap at $1300.
Dildo machines are mechanized pistons that with a latex cock. I think the guys who build these things started off tinckering with train sets, moved up to taking apart car engines and then somehow got sidetracked into seeing females being masturbated by machines, so they began building these gizmos.
We borrowed one such machine from a company called KensTwistedMind.com in exchange for promotional consideration. It can cost thousands of dollars. Only chicks who have money, or their husbands, can afford them.
One of the recipients of this arrangement was the utra-sexy Crystal Gunns, who agreed to try it out in a video.