Um... not at all. On a 200$ snake, charging 100$ just to hold it is insane. Considering a ball python eats maybe weekly (4 weeks, 10$, tops), and needs bedding changed a couple times a week to every couple weeks depending on the bedding (trivial to 2$), and requires about 6 watts of electricity (2-5$).
Anything more than 10% the animal's cost, in this case, is just profit for something that should already have made profit simply on its sale.