Are you talking about just the cost of the film or film and processing? For fresh film, check out B&H's prices with shipping and divide by the number of sheets.
Kodak Ektar 100 is about $2.65 a sheet and HP5 is about $1.14 per sheet on a 100 sheet box. Processing is a whole other thing that can be all over the place. I process my own film so can't really give you a good idea as to how much you would have to pay for processing.
Are you just starting out in LF? If you are you will soon find out the the film is the cheapest part of the addiction