Do we have any idea how much higher the premiums are likely to be?
Google says there are 1.5-3 million insulin users in the USA - lets call it 1% of the population. Let's say that their drugs cost $300 / month, but they pay $100. The extra $200 will be shared between 100 people's premiums, so $2 extra per month.
The media is citing 1.3 million in Illinois alone with diabetes requiring insulin (out of about 12M population; over 10%) and at least some cases where the cost is over $1000 per month. Assuming it averages out to $300 per month as you said, however, that's still $20/mo. extra per person assuming the difference is distributed uniformly across all insured individuals, and that all individuals in the state are insured.
Google says there are 1.5-3 million insulin users in the USA - lets call it 1% of the population. Let's say that their drugs cost $300 / month, but they pay $100. The extra $200 will be shared between 100 people's premiums, so $2 extra per month.