The Texas stat comes from a 1992 Dallas Morning News article. The article is quoted by saying, in 1992, it cost 2.3 million dollars (US) to execute someone in Texas. The phrasing is misleading.
It costs about $22,000.00 a year to house a prisoner in the Texas prison system (TDCJ). That is if they do not have some sort of health issues that require constant medical treatment or surgery. Prison life is hard (for both the inmates and the correctional officers). A life sentence may only be 20 to 40 years depending on the age of the person at the time the start their sentence.
The real cost to the tax payers comes in with the legal appeals that death row inmates automatically get by law. For example - the first thing that happens is the prisoner's lawyer must get the trial transcript from the court reporter. A Murder trial that lasts 2 weeks will result in a court reporter charging the defense attorney about $60,000.00 for the trial transcripts. Then the attorney will charge the State about $200.00 an hour for his or her services in representing the defendant's appeal.
The actual cost of 1 dose of the drug used in lethal injection is about $17,000.00(US) and the one company on the planet that makes the drugs is now refusing to sell it to the United States as the company is located in a country that no longer practices execution of prisoners.