Most sales on DT aren't the percentage sales that involve levels that go up based on increasing numbers of sales, most are subscriptions and the contributor price is a fixed $0.35. I do get occasional $2.00 sales and every once in a while something more, but most of their buyers use the subscription plan.
DT did increased their commissions 10% starting today; I haven't had a sale yet, so my numbers are slightly out of date.
You can opt out of SR-EL sales. It's a box you check/uncheck when you submit files.