Pay for jump pilot Training?!

I have a job offer to drop jumpers in a 182 but they say the "training" is unpaid. In fact, they want to bill me $25 per training flight (which would be about 5 or 6 flights total) because that is the amount of money they are loosing by taking the spot away from a paying solo jumper. I don't have to pay them out of pocket though... after training I just work off the amount. Pay rate once training is over, which only takes a couple days, is $10-$20 per tack hour. It's a sliding scale... A day of consistent fast runs (.3's and .4's) get the $20 rate, slower runs (above .4's) get the $10. Even if you're at the higher pay rate that only works out to about $8 per load. A typical day consists of 4-5 hours of flight time for the jump pilot.

My gut tells me to stay away, but I'm interested in some other opinions.