Even though Medicare Part D provides seniors with some protection, the high costs for some specialty drugs—and the fact that many seniors take multiple medications, with resulting higher odds that they will need one of the specialty drugs for conditions ranging from cancer to rheumatoid arthritis—are driving up the amounts that seniors must pay, despite Part D's assistance.

Kaiser analyzed 12 different specialty drugs, and concluded that seniors could end up paying anywhere from $4,400 a year to $12,000 a year out of their own pockets—and that's after Part D kicks in its share.

Even generics aren't immune to the price hikes, as AARP reported last fall.

Some generics have gone up so much that the Senate Subcommittee on Primary Health and Aging held a hearing on it late in 2014. (Shkreli has been ordered to his own hearing on drug pricing before the House Oversight Committee next week, along with a former Turing colleague, Nancy Retzlaff, as well as the interim CEO of Valeant Pharmaceuticals' interim CEO Howard Schiller.)

Part D, obviously, is not keeping up with price increases such as that for the antibiotic doxycycline, which has recently increased from $20 to $1,849 for 500 capsules.

In addition, most plans use price tiers that require participants to pay coinsurance on expensive brand-name and specialty drugs, instead of copays, but some plans use coinsurance no matter what the drug is.

So hefty price increases on generics as well as on specialty drugs will end up costing seniors—particularly those on fixed incomes—big time.