Henning has told us of the bottlenecks that are causing the demand to exceed supply.
The bottlenecks that Henning refers to are not the only ones.
My source(s) indicate that all the film manufacturers are much more "cash poor" than when film was in its heyday, and all of them are looking at issues of limited numbers of sources for and limited access to required components, aged and/or limited capacity machinery, and much higher distribution costs.
They just don't have the capital to be able to "stock up" on inventory.
Some of the components necessary for Kodak's recently re-introduced E6 films require custom manufacture by third parties, with at least a several months lead time. And the services of the suppliers of those components are in high demand, from customers who compete for those services. Kodak (and others) no longer have the resources to stock-pile those components, and their orders are sufficiently small (and relatively unimportant) that they don't have the necessary clout to ensure priority from those suppliers.
The film manufacturers are looking at 2019 and wondering - will this surge of demand be consistent and growing, or will it be just a short term thing. If the former, than it will be worthwhile to incur the substantial risks of making the large capital investments necessary to modernize and expand existing machinery. If the latter, taking those risks will be a quick way to (another) bankruptcy.
For an example, as I understand it, in 2019 Eastman Kodak sold more 65mm camera film stock to the movie industry than they have in any year in the last 25 years, and there are a number of projects scheduled for next year to make it likely that that will continue next year as well. That being said, critical portions of the manufacturing machinery for that film - the perforators - were the same machines that were used in 1959 when they made the film that "Spartacus" was shot on.
If you want to help moderate price increases, help keep volumes consistent and increasing by buying and using film.