I understand that groups generally have one DM and 4 players, do if you include player options you might sell 5 books instead of one. But that's the shallow, cash-in-now-fuck-next-decade mentality.
Meanwhile they haven't put out a decent adventure in a decade. The internet is awash with people trying to glue their ramblings back into coherent campaigns and running D&D (always a huge time sink) is becoming a worse experience every year as they keep flooding the market with crap.
I love running games but I've come to the point where I'm not really interested in starting a D&D group anymore because of all the bullshit.
WOTC: support your DMs or die.