I don't find it odd that it varies, just that it varies so wildly. well over 10x seems unreasonable. If it is an area that is that expensive, perhaps it makes sense to transport the prisoners a bit to a less expensive area.

There are often legal barriers to transferring prisoners out of a state, not least that it imposes a significant burden on their families who may be unable to visit them (and who have rights of their own, regardless of how one feels about the prisoner).

I should have mentioned that states like NY als have more extensive rehabilitation programs (which cost money); on the upside, as far as I recall NY has one of the lower rates of incarceration and recidivism (but I might be wrong, don't feel like delving into the stats right now).