Exactly crime is a business. as long as someone is willing to do the work and make a profit at it they will do so.
Prisons are part of what makes crime expensive. Another thing is flooding the market with low value goods that simulate high value goods.
Look at car radios. since manufacturer's started putting high quality audio and navigation systems into cars, car radio theft has dropped off considerably. It isn't worth it to steal the radio.
Tv's aren't big ticket items anymore. neither are dvd players. Computers are a mixed bag but even they are so cheap now a days. jewels always will be. Though if you want to protect your diamonds the best way is to put staged storage areas filled with fakes. the crooks will steal the fakes.
Crime falls when the standard of living comes up, and inequality is lessened. As inequality is increased so does crime.