Ajmani, the whole point of this IS to discourage people from going to the mall.

If you have so little money that paying an extra 5 riyals for the first 2 hours of parking at City Center is a problem, then chances are you don't have much money to spend on anything else either.  

City Center is trying to attract people who spend a few hundred riyals each trip, rather than providing a free, airconditioned walking track for people to wander around pointlessly for hours on end.

For me personally, I am far more likely to visit the mall now that I know I am likely to be able to find a park.