CNN just ran a story on incomes of appraisers.  This survey stikes me as a bit overstated. Specialization is key, especially if the focus is on complex properties.
IMHO, I think the appraisers on the residential side that are generating a lot of income, own very large operations with a lot of trainees and are tied in tight with wholesale lending channels. Its going to be interesting to see how these firms do when or if refi or sales business drops off significantly. On the commercial side, its the firms tied in with conduits. With capital in abundance these days, demand for these appraisers is high.
A study on appraiser incomes [Note: Abstract] , done in 1999 at Washington State University, was reported to be the first of its kind.