In my experience, DM's are much more into D&D than the average player (though of the 13 players involved in the 3 campaigns I run, 2 are DM's of their own campaigns).
Players maybe get a PHB (some borrow), maybe get a avatar (about half borrow), and maybe get dice (about half). A few get a few more books. Upper middle spending (own their own basics, but no more) is $35 + $20 + $5 = $60, for multiple years of playing; amortized it's something like $20 a year -- much more is spent on beer and food for the games! Low end spend (borrower) = $0. Highest spend (own stuff plus buy occassionally) = $60-120 a year.
My spend was probably $1000-$1200 a year in the early years of 3.0. It's less now, because there's much less interesting stuff out there. Last month, I went into to FLGS. I bought two issues of Dungeon in one, and a DCC adventure in the other. So, maybe $50 a month, or $600 a year.
So in my world, the DM spends $600, the average player $20, that means 30x as much for DM's, or total spending by 3 DM's across the 13 + me folks in my games = $1800, total spending by pure players = $220, so DM spending is 90% of the total. Seems about right.
WOTC seems to think it's the other way, with lots of "player advantage" books lately, but it doesn't apply for my groups for 3 reasons:
- I'm old school, and I don't play very often. Once every two months in person. Continuously over email, which is so slow and haphazard it equals once every 4 months or so. And 1-2 times a year with my oldest campaign, in another time zone I visit 1-2 times a year. I don't like a lot of unnecessary extra rules and "world changes" between sessions, so I ban everything that's not specifically approved. I also don't like spending a lot of money to "break" my game, so I don't buy crunch books myself either. Instead, I buy TONS of adventures, to read for fun, to run, and to swipe bits from.
- Most of my players don't like spending a lot of money on D&D, and instead mooch off my stuff. I'm totally OK with this, as I'm buying it anyhow, and everybody in my games is a real world friend first.
- My players aren't into 3e ish weirdness. They're a mix of old schoolers who learned under 1st Edition, and brand new players who understand the world to be like LOTR. Neither brand of player is interested in playing half dragon fiendish dire vampire soul thief/accountants in spikey bondage armor.
Somebody like Aragorn only different in X, Y, and Z ways is more like it.