I agree with your assessment of costs and also agree that crime committed by homeless individuals puts a major strain on our judicial system.  However, there seems to be a philosophical catch 22:  We can agree that citing homeless individuals for camping out after hours, and "criminalizing their drug use" does no good for them but how does that translate for the rest of those who follow the law and do get cited?  
I have friends who have been cited for jay walking, open liquor containers at the park, and drug use.  Is it only logical to prosecute them because they can pay or because they are "normal" citizens?  They pay taxes, they contribute to society.  

Where do we draw the line?  Adopting the attitude - "oh they're homeless and they don't have anything so why kick them when they're down is extremely unfair for the law-abiding citizens.  On the other side, we can become a society much like "Gattaca" or the Spartans where we risk losing our humanity.  Where do we draw the line?