A lot, that's all I know. It adds up pretty quick and I don't buy much from shops, so it usually just sits stagnant wherever trainers keep their money. I'll probably waste it all on vitamins eventually, though.
On one version of Black, 107333.
On the other version, 14532 (I started a new game on it recently).
On White, 16320 (again, I started a new game)
On White 2, 76030.
On SoulSilver, 994455 (hooray AR)
On Platinum, 20104.
On LeafGreen, 2500. xD
On Pokemon Rumble Blast, 5,087,009. Because I never buy anything on that game. xD
I'm too lazy to check all my Pokemon games just to see how much money I have in each one, though I can recall having at least close to the maximum money capacity in Pokemon Black. I must be one of the richest people in the Unova region!