The retail price for a 400 foot roll of Ektachrome 100D right now is $475 from Kodak. That seems to be the cheapest price around. It's even more expensive at places like Film Emporium, at $547 a roll.

How many 36 exposure rolls can you get out of 400 feet? Depending on your loader and how careful you are, anywhere from 72 to 80 rolls, based on 18 to 20 rolls per 100 feet. So at worst, that works out to $6.60 a roll. Definitely cheaper than buying remaining stocks of the Kodak E100 still films, but still pretty expensive.

I doubt large studios use a lot of reversal film or pay full retail price for it. The color negative films are far more commonly used, and are much less expensive than reversal film.