As with many medical drugs, the marginal cost of production of the medication is small, but it is dwarfed by the cost of research, trial conduction and FDA approval and is patented. Additionally for CAR-T there is rather intense post-adminitsation care required.
For the pharma research companies to be profitable, they need to recoup the above costs on the limited number of cancer patients there are.
For a widely applicable technology like CAR-T, if you can figure out how to distribute the costs over multiple types of cancers, you could have a much larger pool of patients to distribute the cost over, such that the marginal cost of production is a more meaningful component of the cost to patient/insurer.
Pharma typically spends a lot more on marketing than research. In fact, there is little to no correlation between research costs and the cost of a drug.
There are companies doing research in applying CAR-T for treating animals. This has a much easier approval process since it is run through USDA and not FDA. I'd expect to see faster advancements in treatment and lowering costs and then having this tech brought over to humans later.
For the pharma research companies to be profitable, they need to recoup the above costs on the limited number of cancer patients there are.
For a widely applicable technology like CAR-T, if you can figure out how to distribute the costs over multiple types of cancers, you could have a much larger pool of patients to distribute the cost over, such that the marginal cost of production is a more meaningful component of the cost to patient/insurer.