It's ridiculous that the 5700X3D is $190, but the 5800X3D is still $390-400 if you can find it. The 7800X3D is $400.
Some of this pricing makes no sense.
They are probably just discounting what isn't selling.
There is still demand for the 5800X3D because if you have an AM4 system, that is the - as far as gaming is concerned - peak of the AM4 platform you can upgrade to, so everyone who is looking to stretch their AM4 system a little bit longer for gaming purposes without looking to spend on RAM, a new motherboard, or the hassle of rebuilding everything is going to want that 5800X3D.
There are likely many shoppers looking to get as close as they can to latest gen systems for lass money than actually buying a latest gen system.
$350 may seem crazy for an older 5800X3D, but if you take the approach of, I have a budget of $XX today, how can I make the most of it.
Then it becomes $350 for just a 5800X3D vs $205 for a 7600X + $210 for a decent AM5 Motherboard + $100 for DDR5 RAM.
Now you are talking $350 to get you within 5% of what would cost you $515, and you can pout off that $515 investment another couple of years, and you'll have way more money in two years (Of course you will)
A version of this is why I upgraded the kid and my better halfs machines to 5800X3d's late last year. Minimal effort, relatively low cost, and they continue to have machines that perform very well.
So I think that explains why the 5800x3d remains a strong seller and pricing remains high. No one wants lower end AM4 parts. That's hwy they are cheaper.