I think one of the things that also help piebalds and clowns compared to ghosts and axanthics are the single line. You get a pied or clown and that is what you get. With axanthics you get VPI, Joliff, SK, nerd... With ghost/hypos you can get green, yellow, orange, Nerd line orange... Since each of the lines get generally thrown into one group it brings the group price down. The one exception I have sort of kinda seen is the VPI Axanthic it seems to be maintaining a selling value better than the other lines.