What's the (economical) advantage for a company by paying an employee severance payment short before retirement Given following situation 
A Company has an employee (Bob) who will retire in 3 years. The company decides to save costs and therefore does downsizing. They offer Bob an severance payment in the amount of 3 annual salaries, if he leaves the company.
  Question 
Assuming that Bob is a valuable employee who does a good job - how does it make sense (for a company) to let him go and give him the same amount of money as when he still worked for the company?
 
If relevant: we assume Bob lives in Germany.
If Bob is actually a valuable employee this probably doesn't make sense.
However it is possible that the things Bob is good at just don't have a market any more. So his work could be good but it is not valuable (any more). Training his to do new things is not considered worthwhile with his upcoming retirement.
If he continues to work he probably also needs an office or similar amenities that are not needed if he is let go.
So one could construct examples where it is worthwhile to pay him his full salary until retirement as severance pay but it wouldn't be a typical situation.