The challenge is that the levies in an Estate are for security and all the other amenities, in a stand-alone home any levy incurred would probably be 90% assigned to security, and maybe 10% to beautification (our suburb is like that).
Without doing the math, it is much cheaper for me to live in our home, pay the R550 suburb levy and enjoy a pretty safe environment e.g. my wife jogs in the morning/evening, my kids ride their bikes on the road, many people park cars on the street, our local park is always full of residents etc. Sure, it's not an estate, but the cost is considerably lower I'm sure.