You are completely right that what I was trying to talk about was the purchasing power of money - I did try to imply that there are reasons why money can be created and destroyed (this is true for the numerical case as well). It is a valid point that things can depreciate in value with improvement in e.g. manufacturing process, but I think that is quite independent of people making money - Bill Gates is an interesting example because Microsoft have changed the world in that way. A lot of the very rich do not make such contributions so I do not see how their amassing wealth can do anything other than to take away from others.

It seems very fundamental - maybe I miss something, but if you get money (spending power, whatever) it comes from other people. Therefore people can't get richer without making other people poorer.