they didn't increase efficiency at all, they just increase the amount they were able to squeeze out of the IP. thats not an efficiency vs inefficiency, its n vs n+1.
It's not that they started producing more units, it's that some folks (the ones using the drugs) were taking advantage of a market inefficiency (the insufficiently low price) which when corrected, meant greater returns for Shkreli et al.
Just as when a "retail" day trader hits on a system that enables them to make a large amount of money, they're taking advantage of an inefficiency, and, in a way, helping to correct it.
It's not pretty, but being ugly doesn't make it inaccurate.