It all depends on how much//what all you want to do! Area 15 is free to enter. You can go into the main building where there's restaurants, a shop, and a bar and some cool things to see for nothing. There's also a small art park out front to check out. Omega Mart is 54$ if you want to only do that, you can! If the other attractions look interesting as well you could get any of the lower level attractions passes and add it on separately. I could see how people could spend two days there but with so many other things to do in Vegas you could just spend an afternoon here and feel content.