I agree with what you are saying, but think of it from Gabby's point of view. Why would anyone take a pay cut when they are going into the prime yrs of their career?
Even with a paycut I think he'd have difficulties finding a club willing to pay him what Aston Villa would be willing to.
He has sentimental(not sure if I'm using the right english word) value here which he doesn't have at other clubs.