Your efforts to prop up the GSE talking points do not match reality. Did you not read the AI example of a large firm ( Soliidfi ) ordering 18,000 appraisals a month?
it is not simply dividing 27 firms into some imaginary total. The 27 firms order the lion's share of the volume, and each the 86% of the remaining AM "s have much lower volume. Some have none in an area. My personal estimate, having actually worked for AMC's, is that of the 27 examples, fewer than that have the vast volume in an area, which makes sense, since the national AMC s have contracts with the biggest national banks or online lenders. In some cases, the AMC is owned by a lender as a division.
I already addressed that even if appraisal fees vary by locale, it happens that in any locale, the appraisal fees paid by an AMC are much lower than what a lender pays for the same work when no AMC is used. Market conditions need to be extreme to reach a parity of open market supply and demand, and extreme market conditions are not the norm.
The AMC's need not collude to lower fees. They are smarter than that wrt legal. The fact that the narrow channel of demand gives the AMC tremendous leverage serves to accomplish it. Enabled by the Govt perk of the HUD bundled fee. Which gets a pass from those who scream commie if a working person gets a govt crumb.