Comment by justincormack

Film is manufactured on huge rolls, and is cut down to different sizes and formats, so its not really that expensive on the manufacturing side to support a lot of formats. From the buy side, cameras are expensive, and almost all cameras only support one format. The big change came with film developing labs on teh high street, as when development was at home it was fairly manual, but once it was automated the machines were designed for fewer formats (for a long time 35mm, and often medium format). But even then, the process doesnt change per format and the chemicals are the same, so supporting variation is relatively cheap.