I haven't kept up with graphics cards, but I bought a used Nvidia something-or-other a couple of years ago, GT760 or something along those lines, and I can't believe what used stuff is going for right now on the auction site.

Is it still crypto miners driving the market?  Supply?  Chip shortage like the Fords?

I need a few-years-old midrange Nvidia, or ATI, with 4-6GB VRAM and something that doesn't put out a ton of heat or require a lot of power.  In fact something without board-mounted power connectors would be perfect.

I'm in for $100 or less.  

Any advice?

Advice? Wait 6 months.  Between the miner idiots, shortages at all the major fabs, etc....prices are beyond insane.

Your technical requirements are at odds with your budget.  Once you get start getting into the 4gb or more of vram, even at pre-panic prices you're talking at least $150.  Also cards that don't require an pci-e power connector tend to be at the lower end of the power scale.  About the fastest cards that run solely off bus power are the GTX1650's

Buying used GPU's is a bad idea.  You get a much slower card that's probably been rode hard and put away wet.

Thanks for the reply.  I haven't bought a new computer part in at least 10 years.  I've had a few graphics cards during that time, higher-end stuff from a few years ago, always bought fleabay without issue.  I'll keep looking, and maybe checking locally as well.