The idea that RPG hobby is expensive compared to most hobbies, is kind of silly. If you're into sports, sports equipment is expensive. If you're into motorcycles, snowmobiling, boating, restoring old cars, flying a single engine airplane, or any number of other hobbies, the cost of a single motorcycle, snowmobile, boat, old car, airplane will far, far outcost anything purchased for an RPG (even an entire lifetime's worth of RPG purchases). Most hobbies have a far greater expense to be involved than RPGs, but as you mentioned, some hobbies have even less investment, but I believe those have smaller number of hobbiests, than most hobbies...
If you're playing Pathfinder RPG, all the rules, plus many third party rules exist at d20pfsrd.com, so as long as you have a computer and internet access (neither of which is cost free) all the RPG rules you need to run your game is available to freely access. You never need to buy RPG books to play some games, as long as rules are available for free online. You can even do your dice rolling using any number of free or low cost dice generators. Aside from paper and pencil (and a PC can serve that purpose too), there is little cost behind that required. On the other hand, if you want more tools and assets to better immerse your players, such as miniatures, printed maps, 3D terrain, etc, it certainly can get expensive. However, those are unnecessary to run an RPG game, working only as options for those who want to spend money to make the game more exciting for them.
Simple isn't always better. I enjoy nuance in my games. Sometimes success or failure of a given task is not enough, often I need to know how successful or unsuccessful a given task is achieved - other resolutions to a given task might be available aside from a blanket pass or fail. If rules don't allow nuance then its too simple. Rules don't have to be overly complex, but some level of complexity may be necessary to make for a better play experience to some people. We are all different and have different levels of what we need a game to provide to make the most of it. Simple works for some groups, and not for others.