Please explain that more; it's been bugging me that the legal process could end up costing more money than the total needed to sustain an inmate's life for life.
Housing inmates in general population is dirt cheap. About $30k per head, per year. The fact that so many prisons are now operated for profit should tell you something. Guards don't make much. Food is the cheapest you can buy. Same for medical care.
A death sentence requires more time and money at every phase. Trials cost more (a lot more). Appeals cost even more, and there are a variety of appeals that happen, and they're at both state and federal levels. Then you've got incarcerating somebody on death row, which is also quite a bit more expensive*.
The link Implode posted provides a great deal of info, but one of the most telling numbers in it is the Texas entry. No state has gone to greater lengths to streamline the process. Rick Perry is basing his campaign on how effectively we're able to kill people. Yet even here it costs three times as much to execute someone as it does to lock them up for 40 years. If we can't do it right, why would you think anybody else could do it better?
*There's a wonderful irony about that, in that a great deal of the added cost is to insure that the prisoner doesn't kill himself before the state gets a chance to do it first.