Re: It can be difficult, but..
Money, maybe, but I don't think enough motivation. Put it this way: I'm putting an armed storming of the US SuperMax facility as a matter of WHEN, not IF.
I got to see enough of NZ's prisons visitng a young lad within my family to see how quickly that would fail, and he was only in a place that was "medium security" by NZ's relaxed standards!
Short of tanks and attack aircraft, I am pretty sure they're not getting very far. They may try storming the place with hand-held weapons, but the guards will be laughing at their twitching corpses a few minutes later.
Not that I watch enough TV to know what "supermax" prisons are really like, just seen enough in real life to know you ain't getting without some heavy equipment, and even in NZ you'd be spotted and, well, spotted long before you got it near the place.