https://www.digikey.com/en/products/detail/amd/SK-KV260-G/13...
The price is very good for Ultrascale+.
I think something could made cheaper using an Efinix Titanium chip, someone should do it. Their own dev. board is too expensive:
https://www.efinixinc.com/products-devkits-titaniumti180m484...