I can't find the exact quote (which is annoying), but you'll eventually hear the New-U state it. Something along the lines that they make a huge profit being able to respawn you as you "pointlessly" go about trying to accomplish your goal of killing Jack. Combine that with Jack's massive ego and it becomes more sensible.

"Don't think of the New-U charges as war profiteering, think of them as war...fun!"

ah wow its brilliant, cost effective and evil cool, one of these days i really should play borderlands.