TinkerCAD costs $19 per month for the Personal edition and $100/month for the Startup edition. I'd buy a basic CAD package rather than "rent" one month to month. Three-dimensional printers might appeal to more people at a lower cost, but as the cost goes down I expect more small companies to offer 3-D printing services--perhaps even the UPS Store or local Kinkos-Fedex store could make my prototypes.
I no longer make my own printed-circuit boards because I can get a 2-day turnaround from local shops that welcome small orders. And some PCB quick-turn companies also provide the schematic-capture and board-layout tools for free. Watch the same thing happen with 3-D printing.
It won't be too much longer and hardware design, as we used to know it, will be remembered alongside the slide rule and the Karnaugh map. You will need to move beyond those familiar bits and bytes into the new world of software centric design.
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