Film, paper and chemistry are the only costs (besides time and effort) for about 80 % of my photography. I have an 8x10, too - with a 4x5 back for when I want to use a 16 1/2" lens on 4x5. I've even used the 6x7 rollfilm back on the 8x10, via the 4x5 Graflock.
Originally Posted by fran
There are many reasons besides cost to use a rollfilm back. I've used the rollfilm back on my Linhof with a 90mm lens, taking panned photos of bobsleds in action. Not an ideal outfit, but very effective with a little practice. I've done that with the same camera, a 150, and 4x5 film.