Based on two bedroom furnished villas. Prices vary with the size/style/furniture selected.
Sharbatly - SAR 56,000 - 97,000
Arabian Homes Sierra - SAR100,000 - 135,000
Arabian Homes Andalus - SAR70,000 - SAR90,000
Lotus IV - SAR88,000
Andalusia - SAR 170,000 - 205,000 (3 Room)
That should give you on indication. There are cheaper places, but they lack the facilites provided by the larger compounds.
Good Luck.
Mutt.