How much XP does it take per Paragon level?

Solution 1:

Lots(!)

Molster over at Diablofans made a spreadsheet which details the amount of experience required to get Paragon levels with the new Paragon 2.0 system:

It is worth noting that these levels are in addition the 60 (70 in Reaper of Souls) character levels.

Solution 2:

There is also this chart, which shows the experience needed for each level.

So, you need 10,454,400,000 experience total, from level 60.

From the calculations in this thread, starting from level 60, with full 75% NV buff, to get 100 paragon will require killing approximately 1,327,000 lvl 63 monsters, or 6,534,000 Inferno Hulking Phase Beasts, or 8,167,500 Inferno Dust Imps.

Happy hunting!