All these complicated incentives make it hard to figure out who's responsible, so let me ask a question:
What if a manufacturer lowered the price of insulin to $10 a month and gave no rebates at all? Would insurance companies refuse to cover it and pharmacies refuse to carry it?
I think the problem is that this isn't in either of their interests. The insurers benefit from high prices because it scares people into staying insured and, IIRC, the laws limit the percentage of their profits, so a percentage of a higher number means more profit. The drug companies more obviously benefit from high prices.
What if a manufacturer lowered the price of insulin to $10 a month and gave no rebates at all? Would insurance companies refuse to cover it and pharmacies refuse to carry it?