A magnet zapper runs $450 and upwards to around $700. If and when you become good enough to merit top end motors, the zappers for this job will be obsolete. The zappers are for brushed motors. A zapper, comm lathe, motors, brushes, dyno/motor checker, comm drops, and alignmrnt tools can cost upto $1000.
Brushless is taking, or pretty much has already taken over the motor wars. I probably wouldn't worry about zapping motors. Much less to run over the long run. You just need a Brushless motor and Brushless ESC. Cost around $250 new for both. Motors require minimal maintainance. If you ever need to replace the motor it cost around $75-$85 for a new one.
Hope this helps.