Yes, when they work overtime they get paid more for that overtime than regular time.
The money doesn't somehow make it sustainable for the people burning out their lives. Working 7 days a week, including overnight shifts, for 20 years to collect a pension seems like WELL earned compensation.
That's seems unrelated to "we have so few" and "we enmiserate the one's we do have".
I think rahimnathwani's point was not that they get extra pay so it's fine, but that it seems economically irrational to overwork fewer staff if it's actually more expensive.