So, you have DDR4?
Pick any B550 with a VRM heatsink for $90, a 5600 for $190, and you are back in business.
Get a 5070 or 9070 before GDDR supply is completely gone if you want an actual upgrade.
As for GPU price, that Vega 64 was $500 in 2018. Even a midrange GPU hasn't been $300 since the Radeon RX 480 launched a decade ago.
This is essentially what I did and it worked a treat. Get in while the getting's still good. Having a modern but DDR4 compatible system is not obly a great way to get up and running now, but will help see you through this crisis long term.