IF the price is right, one could buy 9th gen Core i7 CPU.
Since we don't know from where OP is, and what their local (2nd hand) market situation is, we can't instantly dismiss that option either. Just because i7-9700K costs 250-300 bucks in USA, doesn't mean it costs the same everywhere else in the world.
intel portfolio unlike amd has fairly consistent pricing across the regions, and even on second market, intel cpus don't tend to loose retail value the same way as other brands. There also another aspect to this, coffee lake's perceived performance came with a lot of caveats.
In many ways, it sits in similar place as Prescott microarchitecture all those years ago. in mixed workloads it still performes reasonably well, but when avx2 extensions come into play, which modern titles increasingly take advantage of, they flare up like a blow torch.
Maximum memory bandwidth for 9700K is 41.6GB/S regardless of what what memory modules you use. and overclocking bus is a terrible idea as it trickles down to everything else in the system causing huge stability issues.
Maximim memory bandwidth for 12400F, which by all means represents an entry level SKU in 12th gen, 76.8GB/S which is close to double of what 9700K can support. Access latency is also much lower on 12gen.
This may not manifest in in productivity worloads as much but has heavy impact on frame rate consistency in games, and you the list goes on from cache all the way to general connectivity,
It's just a terrible value for the money period, average selling price for new 9700K old stock is around 450 bucks in retail; with 250-300 range being average selling price on ebay ( all regions) most of them previosuly used. Quite frankly even at 200 it's not worth it