I've started telling her how much things cost instead of saying "it was only $10!". Thankfully for me she doesn't like math so she never really puts two and two together
Quite scary though when she buys about $1000 in clothing in a single month and doesn't even realize she's spent more on clothes alone than her entire month's income. Her dad still pays off her credit card bills. Age 22, and she hasn't felt "economic stress" yet.
Lately if she gives me crap for spending money on the tank, I tell her at least it's not a $180 shirt that's only been worn twice in the past year
. Most of my large tank purchases will be around for at least a year, if not five.