It really depends on how you do it. You can waste a lot of money on your equipment. A good air mattress can set you back hundreds of dollars.
But for most items there's also a fully functional cheap solution. A simple camping mat costs about 20 dollars. Living in central Europe there isn't really a whole lot of wilderness for me to explore. So when I go camping I basically go from one paid camping site to the next.
I imagine it would be quite a different experience in the largely empty countryside of the USA where you might even hunt your own meals.