You've obviously not played any modern RTS - Dawn of War, World in Conflict, Company of Heroes, Supreme Commander, etc. all have fixed locations that provide income that can not be destroyed. It's a system that provides more harassment than a finite, worker based system, not less.
ehm you can destroy the mass extractors and power generators in supcom; you also can destroy the upgrades of control points in CoH and DoW (granted, they do give a bit for just controlling it). But how are the mass spots in Supcom different from the undestroyable crystals in starcraft, and then you also have workers which reclaim stuff which are an major part of the economy in supcom.
I wouldn't rate WiC as rts either, its more of a team-based action tactics game but CoH is a very traditional RTS.
In Demigod currently you gain more gold if you control more gold mines and you also gain more gold when you kill more minions (actually when you are nearby) and when you kill Demigods (with lasthit). One of the citadel upgrades also looks like it would increase gold income and iirc there was something about QoT being able to generate gold somehow.
I currently don't have any idea how additional economy stuff could be added in demigod except for being able to temporarily destroy gold mines with either normal damage or a special explosives item (with a long casting time). The mines would either just appear after some time again or would need some money to be rebuild.