Planes get grounded when they have missing or nonfunctional parts. E.g., commercial jets can't fly if the toilets don't work, even though the toilet is not critical to aviation safety.
Imagine you have four multimillion dollar aircraft that can't fly because some small part that is out of production broke. You need those planes to fly missions. How much would you pay to put them back into service?
I think the problem is that they're so disconnected from the value of money that they are willing to pay that much.