Recently I stumbled upon the tact that the market is flooded by second hand Intel Xeon processors. These CPU's are only a few years old, and offer tremendous value for money. They are sold everywere, from alibaba / aliexpress to ebay.com.
Rumor has it that these Xeon CPU's are coming from the big cloud players like AWS, Azure and Google.
Not sure this is true, but several 8-core E5 Xeon CPU's can be obtained for about a 100 bucks.
Just an example:
Take this 8 core - perfect fit for virtualisation: https://www.ebay.com/itm/Intel-Xeon-E5-2680-2-7GHz-Eight-Core-8C-CPU-Processor-SR0KH/401447565673
Perfect for a homelab with 16 threads, just buy two of them if it's not enough for you!
See for more details: https://ark.intel.com/products/64583/Intel-Xeon-Processor-E5-2680-20M-Cache-2_70-GHz-8_00-GTs-Intel-QPI
Still a respectable performance compared to current CPU's: https://www.cpubenchmark.net/cpu.php?cpu=Intel+Xeon+E5-2680+%40+2.70GHz
32GB of memory for these CPU's isn't expensive either: https://www.ebay.com/itm/32GB-4X8GB-DDR3-1600MHz-ECC-REG-MEMORY-FOR-ASRock-EP2C602-4L-D16-SSI-EEB-Server/162349088753
The most expensive part could be the motherboard, with single or dual FCLGA 2011 sockets. There are still a lot of motherboards with the Intel X79 chipset available, and this is a perfect fit in my experience.