Depends in large part on location. Cost of living is much higher in some areas than others.
^^^^^^^^^^
Around here, 100,000 would be a reasonable dividing line (though of course it is ridiculous to make a sharp distinction at some particular income level). But property values around here, though increasing, are still far below the national average.
In general, anyone whose yearly salary is higher than the average cost of a house in the area would be in my opinion defined as being at least modestly wealthy, especially if they don't have children.