Some of the reasons for shortage/price of film explained in this video
https://www.youtube.com/watch?v=Lyb70T6ecqkIn short (and I've probably missed important points),
- Capacity reduced following decline of sales due to digital, including scrapping of machinery to produce film, and shrinkage of numbers of people trained to use them. Also financial difficulty, bankruptcy of producers. Same applies to suppliers of raw materials dependent on film industry.
- Now that demand is rising (see Cudzo's observation on price rise of 2nd hand film cameras), there just isn't capacity to match demand