Yes, this is an important factor without any question. And it has nothing to do necessarily with the country being rich or poor - Norway and The Netherlands are both rich countries, but the per-capita income is lower than in the US. However, wealth-distribution is much better and crucially poverty levels are much lower.
And still, if I remember correctly, in the US prisons are some of the most expensive in the world. I'm at the very least pretty sure they have comparatively many people in them. The prison industry in the US is huge. Doesn't necessarily mean that the system is fundamentally broken, but I am getting the impression that there are too many people benefitting from prisons. I'm just waiting for some kind of scandal to break out similar to the cigarette manufacturor scandals.
Here most common thing to go wrong is that someone who is in a curative state of imprisonment is allowed outside of prison with caretakers sometimes escapes and in rare cases does something bad. The big question here is whether or not you should give up on trying to rehabilitate 90 / 100 criminals just because 10 / 100 is going to do something bad again. Repeat offender stats do differ for various crimes. If I recall correctly for murder it is actually quite low, and for sex offenders it is quite high (which is one of the reasons why they are registered in most countries).
