I would think it’s more about economy of scale. If you tried to build a car without any of the standard parts being available, it would be expensive.
One likely significant factor is the Baumol effect. As mass-produced things get cheaper everything that requires a lot of manual labor gets relatively more and more expensive.
This is basically the Abbott baby formula shortage but for this other critical product. Instead of having a large market with more competition the US has its own special sausage.