Cheapest and highest quality film is Kodak 5222 , short end bw movie film. But I dont know its ASA setting.
Jnanian and many others uses 400 ASA film at 50 ASA setting without problem. Short end movie film costs half an dollar , may be 1 dollar per 36 35mm roll , comes from Hollywood as much as you want and damn quality. Processing and everything is the same with 10 times more expensive films.
If you are interested in , search ''short cut movie film or short end movie film'' They will find you if you whisper to your computer