Well, not really. During the time where you're building up those 50 'lost hours', your body is performing worse. What you owe in sleep you'll (immediately) pay for in reduced quality of wakefulness: lower mental acuity, worse immune system, poorer physical performance, slower recuperation, etc.
It's both better and worse than actual numerical debt. Paying it off is painful and slow, but you don't have to pay off the original amount.