The company that makes Tobi, does have something called the tobi foundation to assist with excessive copays if you can't afford it. It is based on income (we're no longer eligible) and you have to go thru the CF services pharmacy, but it's well worth applying for. Because our prescription plan requires us to pay $15 copay plus 20% with an out of pocket max of $1000, the first time I picked up DS scrip, my cost for a 28 day supply was $536.
At least I'm usually prepared at the beginning of the year and we have a flexible health savings account thru work, but it's still a bit of a shocker. Between that and pulmozyme, we've usually met our out of pocket maximum for prescription meds by February.