In creating a balance sheet to send an expat on an overseas assignment, what do you do when housing costs are less in the host country?

In creating a balance sheet to send an expat on an overseas assignment, what do you do when housing costs are less in the host country? The examples we are given to host country is always higher so we add the difference as allowance, but what if it is less with no allowance to add?

I am sending my ny expat to spain. housing in ny is $2095.97 but the same type of housing in spain is $984.17 per month a difference of $1111.8. what do I do with the extra money the expat will save here?