Sorry to bring this back up, but I have been worried I got my figures wrong.
Lets forget and ignore the figures I posted and just take two known amounts.
Above you stated that to reach level 819, you need 63,862,000xp.
The Game guide states to reach level 800 you nees 54,312,000xp.
By subtracting the numbers, you get a difference of 9,550,000 xp, so that is approx. an average of 502,632 xp per level.
As we know that the amount of xp increases per level, so even just adding 502,000 6 times to the 9,550,000 gives at least a total in access of 12,500,000 points to go from level 800 to level 825.
So IMHO the figures I posted earlier are correct and I am not going mad
