This definition of "wealthy" seems really, really arbitrary. My ancestors made a living by exporting lumber which was chopped by hand, and came close to dying of cold and hunger four or five times during the early 1900s. By that measure, we are all living like kings.

You could live comfortably for the rest of your life on much less than $10MM in assets, even in the absence of an income. So I'd say if there's an absolute limit to "wealthy" in our geographic region, it would have to be "don't have to work for a living", which would be around $1-2MM for a middle-class lifestyle and a 4% annual return on capital.