Only if you let the appeals drag on and on and on and on. Texas got tired of that stuff and after the Texas Seven were recaptured, fast-tracked appeals. As a result, the costs have dropped precipitously.
IIRC, it is going to cost less to finish executing the Texas Seven than it would to house them for the rest of their natural life expectancy.
Good example, not typical. California is a great example of the other extreme. It cost California approx. 73K per year to keep a prisoner, yet it cost California over 373K per year per prisoner in court and lawyer fees for death row prisoners.