The normal price for RTX3060ti was 400$, that was the announced price from nvidia but now it's almost 800$ and some are even selling over 800$ but if you don't mind buying the OEM variants you can still get the around 400 to 450$ on ebay
I'm always a fan of Nvidia graphics card because they always have better cooling than AMD
Where did you get those price from ? Ebay? Well they are too good to be real, a RTX3060ti costs not less than 800$ today, if those prices are real they should be sold out already, be careful they might be from unverified sellers or scammers I'm always a fan of Nvidia graphics card because they always have better cooling than AMD