Probably the initial value of the high 9 1929 cent was derived from what collectors were willing to pay for one when the variety was discovered. Without actual mintage numbers, my guess is that the value compared to the low 9 variety will stabilize over time to some value dictated by its perceived relative scarcity. Hopefully SPP will chime in here - I think he recently finished his search for a red MS example.
BTW, 50 cents well spent!