Isn't the process for killing someone more expensive than actual imprisonment?
According to pro-death website it was about $86.09 for the lethal injection. Now to house a prisoner, according to something pulled from google, it costs 60,000 USD a year to feed, cloth, and house a prisoner for a year.
You would also have to factor in the cost of housing them in jail for the time spent waiting for their courtroom trial, and transportation expenses to the courtroom from the jail and to the prison after sentencing as well as the costs of cremation/burial, and the cost of each final meal they had. Plus the cost of them waiting each year on deathrow for their execution.
That Modesto guy, Scott Peterson, they guy who killed his pregnant wife in 2004 and dumped the body in San Francisco, sentenced to death row in 2005. He is still alive and waiting there.