Cost of common DYI engineering project?

Hi there, I am inexperienced in engineering and building things in general, but I am trying to start a tech company anyway. I am currently in the process of determining the budget cost of building a prototype for various designs of ideas. So I am wondering if you can tell me how much commonly used tools and materials of a DIY mechanical/electrical engineering project might cost. If you don't know because estimates can vary, then tell me from your personal experience how much your list of tools and materials costed you on various projects that you've done. Thank you!