The worst thing about the death penalty isn't even the cost but the unaccounted-for negative externalities. Committing crimes carries a heightened risk of death; if the state is also likely to sentence you to death, there's never an incentive to peacefully surrender, and no risk to get caught is too small. A meth dealer is in constant danger from their customers, competitors, the local mafia, the local mafia's competitors, other criminals for whom they present a high-value target, civilians and cops. If the death penalty is a possibility, there's nothing they wouldn't do to not get caught. But if it isn't, giving up, making a deal and getting out in 10 years and help your kid through college with your meth money is more enticing than rotting in a landfill.
The same goes for other crimes. So you've broken into a house and the owner is there and he's got a gun.
Option 1: kill him, kill his wife and two kids, set fire to the house, kill their toddler, cat, and a retiree in a neighboring house (which has caught fire) via smoke inhalation, catch an uber, kill the driver.
Option 2: shoot him, then run the fuck away.