It's hard to tell what are the best deals, but there are a lot of Black Friday deals out there. It depends a lot on your requirements what is the best deal. More requirements usually mean more money to dish out, even when it's Black Friday.
If you're looking for a price point under $50, there are the following.
Sampletekk through AudioPlugin.Deals, roughly 30 bucks for four pianos.https://audioplugin.deals/deal-1/
Production Voices do have a few at this price point. Assuming you don't have Kontakt 5/6 full version, these are their Sforzando libraries. No need to buy an expensive sampler, they run in the free Sforzando Player.https://www.productionvoices.com/sforzando-libraries/
They also have some libraries for Kontakt full, if it so happens you own it.
Native Instruments have some pretty good libraries at half their usual prices. That's a bit over $50, but I would say they are probably of better quality than the above piano VSTs, though that is always subjective.https://www.native-instruments.com/en/catalog/komplete/keys/
These are just a few, there are probably more. A few members here are diligent to report on deals, myself included. If you look through the last few pages in this forum, you'll find some more deals.