I often talk about the cost of things and relative value with my children.
Even if I can afford things, I make a point to tell them why I don’t think something is good value.
If they ask for treats, they get one of I will maybe mention how I don’t want to waste money on xyz.
Not in a negative way, but to have an awareness of value.
Then gratitude is really important. To make children appreciate good experiences and not take things for granted.
Also, to help around the house and not be oblivious to how the world is not the same for everyone.
If like to put value on time and money and make a reference to the hour it takes our cleaner to earn her rate if they want to spend waste money on something very silly.
Finally, take them to a soup kitchen to volunteer if you feel they need a contrast form their own bubble.
Or take them to less affluent areas of London for a contrast and reality check.