I don't recall if there was addon like that - I thought I had seen one, although I can't seem to find it so maybe I was mistaken. Would it work to simply use the orders of magnitude as units to make numbers considerably easier to process mentally? That is,
1,000,000 = 1M (1 million),
1,000,000,000 = 1B (1 billion)
etc.
If so, a quick search on Curse (for "artifact") netted some addons:
https://mods.curse.com/addons/wow/artifact-power-helper or
https://mods.curse.com/addons/wow/totalap (There's more, but these two show units like that)
Where do you want those numbers to appear? If you want to replace every mention of them it might get tricky, but surely you can just ignore them if there's an overview of each item being provided?
PS: Maybe this works, too? -
http://www.wowinterface.com/forums/s...55&postcount=2