Quote Originally Posted by Deus ret.
And I don't quite get the point why players wouldn't want to upgrade to a fortress in the Sahara if fortifying a province actually becomes cheaper.
As of present there's absolutely no reason why a player wouldn't upgrade their castles in "dirt" provinces (well, if you really want gold armoured Saharan cavalry )
If you needed to upgrade to 80% farming before building the citadel, the Sahara or Cyraenica would probably be your last province to upgrade, because the farming upgrade there will take an eternity to return the costs.