Unsurprisingly, this is (yet) another giant lie.
The BA website shows tickets on sale, right this moment, on this route (LHR to all NY airports), for today, for £1,581 economy (and £6,638 business). That's the same for every single BA (and codeshare partners) flight today, including the first flight leaving at 08.25.
And we already know that Knox and her family were upgraded at the check in desk by BA. So the correct figure would be £1,581.
Plus we also know that BA assisted in the fare in any case. So the actual price paid per ticket by the Knox family would likely have been much lower than that.
I simply cannot be bothered to screen-print this, but if you absolutely insist I will do so.
Why do you continue to issue forth these sorts of lies, Vixen? I'm genuinely interested to know.