Making something for $?

I got all the tools to make electronic stuff, but I'm having a hard time trying to figure out something I could make to sell for $$$, any suggestions?

I've been waiting for a time machine to go on the market, I'd be willing to spend a lot of $$$ for it.

In all seriousness, if anybody had an idea to make money, I'm sure they would be the ones taking advantage of it!

I'm not talking about billions of dollars here, just a little gadget or something to sell for like $20 or so bucks.

Ya, again, somebody would still make it. There are plenty of people selling whatever small products they can possibly get out there.

I think the best way to get something other people will pay for is if you can identify needs in niche markets that you have other interests in. Like if you;re into cars you can identify performance products/display items/loggers/controllers, anything that would be useful that brings something interesting.

Will anyone buy it?
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I guess this all depends on how well you can make something and how much it costs. Here is what I am looking for https://www.electro-tech-online.com/threads/thermostat-humity-snesor-display-etc.97837/. Tell me if you can build it and how much. I need 4 right now and possibly several more.