Try www.rodagolfcourse.com they have previously offered golf packages to non owners at Roda or try the many green fee agencies such as murciagolf, 525golf, Costa Calida golf, never pay walk in golf course prices.
Roda and Polaris courses are far superior to Sierra and costs in the region do reflect demand, the courses are generally busy with more Scandinavians taking up the game keeping the tees ticking over.
Twilight golf is always better value.
ive just returned from Belek in Turkey which is regarded as incredible golfing value but even here you will pay 80-120 euros per round for extra golf above package.
its all about demand.