I think I would put it down to 'one of those things'. I am sure there are times you have, without your knowledge, been overcharged, or short changed etc. I think these things balance out (a few weeks ago I was charged twice for the same item at a grocery store (guess she double scanned it) but as I have also been undercharged for things there in the past (when I look at my receipt later, rather than notice at the time), I figure it balances out.

On the expense thing, I know several companies where the spouse's expenses are included if, for example, the spouse is there to entertain clients as well (hosting dinners in foreign cities etc).