DYI Custom Build estimate

You are asking a question that is impossible to answer with any accuracy. All of the items you list come in a large variety of sizes, prices and options. I suggest you start with one system and research the various options. You can search this website, supplier sites, new and used RV sites and so on. Each of the systems in an RV is a project in and of. For instance, the electrical system usually involves separate AC and DC systems, AC to DC converters, DC to AC inverters, various battery configurations, wiring issues and so on. My first DYA conversion started with a bed and basic DC electric system powered by a 12 volt "house" battery. Eventually I added a sink which involved a fresh water tank, plumbing, a pump and a drain system. After using the vehicle for a season I decided I needed a porta potty which worked great. Finally, I added a propane stove top which involved plumbing a gas system. These system evolved over a couple of years. Be careful with safety issues like smoke, gas and carbon monoxide detectors and safe wiring requirements. After camping in my DYA RV for a few very fun years, I ended up buying a used LTV B which I really like, but I do have a special fondness for my homemade RV. Good luck with your project and have fun.