Given the price of the trip ($489) and the number of riders, a $50 "donation" from a chaser does far more for his conscience than it does for the bottom line. I refuse to accept them on those rare occasions when they're offered.
Greg hints at the real issue: what is a charter participant paying for? Exclusive access to the train, or just to the organized runbys for the group? While no chaser should expect to be included in the group's runbys unless he pays full price, as an operator I don't worry about the shots a chaser gets between runbys. I figure we're paying to GET pictures, not to prevent OTHERS from getting them.
But some paying participants do worry about it. I had one guy write me a letter telling me an entire trip was "worthless" because non-paying chasers got a few inferior shots. And I was on one photo special during which the operator spent the whole day obsessing about sticking it to one chaser in particular, and because of that caused his customers to miss the best shot of the day (to make SURE that the chaser didn't get it, either). He lost a lot of customers, permanently, that day.
To each his own, I suppose - my slides are no worse because, a half-mile away, someone took another photo. This isn't a zero-sum game, and his lens isn't sucking up my light.
Stay away from Chris' photo stops, and shoot to your heart's content. And save your pennies for next year - Chris runs a good trip.
JAC