Contributors' payments are based on the amount per credit that the specific buyer paid, so yes it fluctuates.

Yeah, royalties fluctuate a lot there.

Isn't that so at IS also?

for 2010 credits the variation is:

maximum cost is 1.25/credit - max return 50% = .62 per credit

minimum cost is .77/credit, min return  30% = .23 per credit

(for independent)

older credits may be worth more or less.

for subs packages the return varies from .35 to 1.05 and the cheapest the buyers could get the images are about .20 per image. The most expensive for maxing out a subscription is around .43 per image. Obviously if all of the subs are not used DT makes a lot more.

edited to include subs