That's a good analogy between building wheels and light sets.

I recently bought a little voltage regulator which is half the size of my thumb. It has a USB jack. I got it directly from one of those Chinese vendors. I might have gotten it on ebay. As soon as I got it, the vendor wrote to me asking for feedback on how well it works. I may never use it. I got it as a curiosity. Maybe I'll try to build something with it. I'm not even that inclined, electronically.