Well, Carter releases range from 110.00 - 210.00 for back tension releases. This model, the solution 2.75, sells for around 175.00. I would guess you could get 100 - 150 for a hand made custom built back tension release.
As far as drop away arrow rest I would have to say right around 80.00 - 100.00 seeing as how the quicktune 4000 sells for 85.00, the MZE sells for 90.00 and the PSE goes for 75.00