My first "wow we're well off" moment came the first time I went on holiday to India, when I was around six years old. Once you actually see the reality that some people are having to live in there, it's impossible not to appreciate what you've got - even if by Western standards you consider yourself to be poor.
But aside from that one, I had a "wow we're well off" moment when my mum was trying to pressurise me to go on the school ski trip, and I didn't want to. And a few days later I heard my dad talking to his friend, who said that his son (same age as me) had been pleading to be allowed to go on his school's ski trip. And he told my dad that he didn't know how to explain to his son that he couldn't go, because they didn't have that kind of money, as opposed to not being "allowed" to go on the ski trip, as though it's something bad.