He specifically asked to have them “designed, developed, and prototyped”.
He didn’t ask for a sketch, he asked for a concept, which has been refined and built - forgetting what his “new features” that he wanted added were, implying there was some level of development beyond your $12 pair of injection molded pharmacy glasses.
I don’t know about you, but for ~$300-600 after taxes you’re calling a bunch of professionals with years of experience fools? I’m not sure what you consider your time worth, but even if you assume an intern’s time is worth $12.50 an hour that is optimistically a weeks work, which is enough to crank out some sketches, maybe an illustrator rendering or a simple CAD model (not including any of the detailed work for mechanisms which would be much more time consuming).
No one was condescending, and anyone who has taken on work with clients knows that a client with a false expectation is bad for the industry. Just look at what happened to graphic design - now anybody can spend $50 on a logo design from 100 designers in Asia running stolen copies of Photoshop, 99 of who won’t receive a dime. It’s bad business.
ID is not a “cheap” labor cost. It’s fine if you want to take on a side project for a buddy pro bono or for a few dollars. But you can not run a business with the overhead of computers, expensive CAD and design software, materials, etc at a rate of $12.50 an hour.