There's no way the NSW Government is going to pay anything to relocate anyone away from Bankstown.. they'd rather it die naturally than do that.
One proposal for a relocation of Jandakot was exactly that, the sale of the original site covering the cost of the new airport and relocation. That was ended as the businesses did not want to be significantly further away from Perth, especially the aeromedical services, as well as the new site having significant opposition to a new/busy airport at that location.