I bought the 55" 6-series for $499 - $20 extra coupon from Costco online during Boxing Day. It hasn't gotten anywhere near that price since. That said it's a great TV $599 is more than reasonable.
My only complaint about it, as the hardware and software are otherwise without flaw, is that it doesn't play too nice with Google Home or Alexa. The benefit of Android TV (e.g. Hisense) is a bit better integration. But many people won't care.