I was taught that the last drop of ketchup (or anything) costs exactly
as much as the first drop cost.
When I want to make a purchase, I always figure out how many hours I
had to work to earn the money to buy something - and is it worth working so hard for. That sure stops impulse buying.
I was taught, and taught my children, that they could borrow money from
me anytime but that I wanted them to repay it every week - even if they gave me a quarter a week - . And now I see that my little Grandkids have the same options.