Arguments over the moral validity of capital punishment have likely been discussed since the beginning of civilized culture. However, one aspect of this debate that is not commonly discussed is the economic dimension of the issue. The public generally believes that execution costs less money than paying for a lifetime in prison. But, research into the topic reveals that conception to be incorrect.
Capital punishment is much more expensive than keeping a criminal incarcerated for their life. The first and most commonly cited reason for the death penalty being more expensive is the actual process of killing the criminal is very expensive. According to an independent study, a criminal execution costs around $24 million in Washington from start to finish (although, capital punishment costs in Washington do seem to be slightly higher than in other states). For comparison, estimates on the cost of incarceration vary, but the average cost to incarcerate someone seems to be somewhere between 30 and 45 thousand dollars per year.
There are many reasons for the difference in cost, but it goes beyond obvious factors like the chemicals used or the medical professionals who are paid to carry out the executions.
One example of a reason behind the immense costs of capital punishment is the cost of the legal proceedings. In Washington for example, a murder case involving the death penalty costs about $1 million in legal costs more than a murder case where the prosecutors do not seek the death penalty. Additionally, prisoners on death row are commonly held in jail for multiple years during the lengthy appeal process involved with death penalty cases, and must be kept in very expensive high-security prisons after sentencing until the date of their execution.
Therefore, when taking into consideration the sentence for a criminal, the cost minimizing approach is to incarcerate the criminal for the rest of their life.