Peters' absolutely rocks. I cannot say enough good things about them.
Call them. Ask for Brad Stallsmith in the Cutlery Division. They will hook you up. Sending 20 blades at a time will be very cost-effective... one or two blades, not so much. As Jasper said, they will send you an invoice/bill when they return your blades. It generally takes three weeks from the day I send a batch out until I get it back.
I don't really know their pricing structure, but I can say the batch of two dozen blades I got back earlier this week came out to roughly $8/blade, including HT, tempering, cryo, and Rockwell testing, and return shipping. That was for a mixed batch with three different steel types. (air- and oil-hardening, different tempering requirements, etc.)
You simply cannot beat that price, even without considering the very high quality of their service.