Broek is correct. Mike Lardy has some of the best methods on collar conditioning on tape. We also prefer his conditioned retrieve (force fetch).
I obedience train for competition too, we use clickers for postitive reinforcement. The nice thing about the e-collar is that it allows you to shape a behavior and then add distance.
The Dobbs tapes are okay but I like Lardy's better.

I belive I gave $175.00 for my Dogtra NCP 200 Gold last year.