Just drop their insurance. You'll save money regardless, from the sounds of it.

With respect to the pre-existing conditions, only you can make the decision if 3 months is too long. Given the cost of insulin, I would imagine it might still be cheaper to pay for it out of pocket for a few months.

I pay $300/mo for my BCBS insurance, for just me, and I've got enough pre-existing conditions that other insurance companies won't cover me.