an adult diabetic can go thru 2-3 vials a month. lower quality walmart insulin for uninsured folks is "only" $25 a vial, but it's not as good at managing blood sugar swings as any other kind.
with insurance the good insulin can go for $300 a vial, which the insurance may not cover the whole cost of.

so $50-$900 a month is the consumer cost depending on whether you get the good stuff or the cheap stuff.

legislation is starting to help bring that down, however.