On most devices, IMEI numbers are traditionally burned into a soldered IC, are non-reprogrammable chips, and the numbers cannot be changed, without replacing the phone's main PCB.
There won't be criminals specializing in reprogramming, if the cost to reprogram is so close to the revenue to be gotten from reanimating a stolen phone
this is completely false. Don't spread bad info. Google "how to reprogram your IMEI" I'm not sure the legality of posting a link to this kind of stuff. Please educate yourself before making false blanket statements.
Writing software is more fun than working.