Long, long ago, there were "daylight packs". I just translated that from the german word "Tageslichtpackungen", maybe there was something similar available in other countries. They were cheaper than real 35mm cartridges because it was just the inner part of a cartridge - the film on a spool - packaged in light-tight paper. That must have been in the 50s and early 60s when film was so expensive here that people tried to save as much as possible.
I don't think that it would save much money if a film manufacturer omits the metal canister of a 35mm cartridge.