The following is from http://www.deathpenaltyinfo.org/costs-death-penalt...
Financial Facts About the Death Penalty
Report of the California Commission on the Fair Administration of Justice
“The additional cost of confining an inmate to death row, as compared to the maximum security prisons where those sentenced to life without possibility of parole ordinarily serve their sentences, is $90,000 per year per inmate. With California’s current death row population of 670, that accounts for $63.3 million annually.”
Using conservative rough projections, the Commission estimates the annual costs of the present (death penalty) system to be $137 million per year.
The cost of the present system with reforms recommended by the Commission to ensure a fair process would be $232.7 million per year.
The cost of a system in which the number of death-eligible crimes was significantly narrowed would be $130 million per year.
The cost of a system which imposes a maximum penalty of lifetime incarceration instead of the death penalty would be $11.5 million per year.
(Commission on the Fair Administration of Justice, June 30, 2008).
new study released by the Urban Institute on March 6, 2008 forecasted that the lifetime expenses of capitally-prosecuted cases since 1978 will cost Maryland taxpayers $186 million. That translates into at least $37.2 million for each of the state’s five executions since the state reenacted the death penalty. The study estimates that the average cost to Maryland taxpayers for reaching a single death sentence is $3 million - $1.9 million more than the cost of a non-death penalty case. (This includes investigation, trial, appeals, and incarceration costs.) The study examined 162 capital cases that were prosecuted between 1978 and 1999 and found that those cases will cost $186 million more than what those cases would have cost had the death penalty not existed as a punishment. At every phase of a case, according to the study, capital murder cases cost more than non-capital murder cases.
Of the 162 capital cases, there werer 106 cases in which a death sentence was sought but not handed down in Maryland. Those cases cost the state an additional $71 million compared to the cost non-death penalty cases. Those costs were incurred simply to seek the death penalty where the ultimate outcome was a life or long-term prison sentence.