OP, you are asking too much. I sold my $1500 2011 60 inch ST30 for $150. Bought me the 2013 65 inch S60 for $200. The only plasmas thay can fetch $300+ are the final year models which matched the Kuros in terms of picture quality. Those are the 2013 VT60 and ZT60.
I currently own the 2013 S60 and a Sony A80J. The Sony A80J is barely even better than my S60. Do not buy into the marketing of 4k, Dolby Vision, future proof, etc. I would use my S60 over the A80J in a heartbeat if only for one thing. Input lag. I game a lot and input lag is an important feature.
However, HDR and Dolby vision is where you start seeing a larger leap in technological advancement. But there is hardly any content and is still in its infant stage.
Plasmas is an amazing technology. It it just not cost effective. Plasmas has superb screen uniformity, superior motion, organic picture quality, wider viewing angles. The downsides are weight, heat, only 1080 vs 4k, line bleed, input lag for gamers.
Plasma still holds up very well today. Especially if you mostly watch 1080p content. 4K is only slightly more better. You will not even see a difference if you sit more than "x" amount of feet from the tv.
Also, DO NOT BUY a tv this year. So many quality control issues have been problematic due to covid.