Cash and equivalents: 203,970,084,062 as of last time I logged on each of my alts.
That's subdivided as:
135 bids in the AH for 1bn apiece on items that currently do not exist in the game
20 emails for 999,999,999 a piece (will move these to bids at some point)
48,970,084,882 inf spread across 129 alts
I'm not counting inventory, just straight cash, homie (h/t Randy Moss).
EDIT: I know, I thought it would be higher too!