I've looked at them... but 100pcs isn't exactly considered a "prototype run". It's more of a production run.
I have a PCB design, I've etched it manually and it works. I want to do one professional prototype board. If I'm satisfied with the text, layout, quality, etc... I'll do a production run of 25 or 50 boards for my initial batch.
It's doing that single prototype "demo" board that is very costly.
After shipping, setup fees, minimum quantity order, the quote is anywhere from $75 to $150 for that prototype board.