WalMart is still a great deal for Super 8 carts or 25 foot regular 8 (or DS8) Kodachrome. $4.88 per roll. I don't know about 100 foot 16mm film.

If you send your K40 or K25 cine film directly to Dwayne's, it'll cost you $9.00 per roll, but you get faster turnaround by almost a week.