It's 20 bucks to go up there, honestly the view is okay but it's not really worth it..
Here's a tip: If you want a 360° view of the skyline, go to the Helipad Lounge, it's a rooftop bar on top of an helipad. Same price for entry as the Petronas, but you get two drinks free!
Not sponsored, by the way. But I wish I was.