Take a look at the rulings of the federal appellate courts in the 2 nd, 4 th,
9 th and 11 th circuits. Most of them address mark ups, but you might find something on non payment. The section of RESPA that you have quoted seems more punitive to offenders than compensatory to third party subcontractors. The best way to find out would be to file a complaint with HUD for non-payment, and see if HUD will act on it.  We may all be pleasantly surprised.