Wealth and wealthy are two different things. Although I’d submit that most people who don’t think they are wealthy, really are.
Wealth to me is value. Everyone has some of it. It may be a person, a skill, a talent, a thing, a technology, a service, etc.
I definitely agree that your philosophical approach makes the definition akin to ‘happiness,’ which I think is a good way to look at it. Happiness definitely has a lot to do with attitude and a decision to be content. I personally love design and awesome stuff, but I don’t know if they make me ‘happy’ per se. I’d say they give me pleasure, which I think is something different. However, I would say that design, or the process of creation, makes me truly happy.