If I hear another plaintive cry of "Oh, ze core books are so expensive!" I will probably mutter something sour and post a criticism.
Do the mathematics. You spend $100 on the Third Edition core rules. The revision happens three years later. If you play the game once a month, for three hours at a time (and I am deliberately undercutting these numbers for the sake of the point), that means that you spent $1.08 per hour to play a great game.
Most people will spend much more time playing the game, lowering that per-hour price - and yes, it's true that they'll also spend a lot more money on their sourcebooks.
I know it - apart from the core rules and a few third-party books, I have eight hardback D&D books on my shelves, most of the products published after the revision. I'm in Australia, so even the relative damage to my finances is worse than any American can claim. Even in American dollars that's $268 since 3.5 came out, and sometime this month or the next I'm getting Serpent Kingdoms and the Planar Handbook.
I play D&D about three times a month, more or less, for a total of about 15 hours (at a conservative estimate, since it's usually more like 18). The revision came out about a year ago, conveniently enough. Call it 180 hours of play, stacked up against US$380 worth of material.
That's still only US$2.11, or about five bucks in Australian money, an hour. As if that's not worth it - and when you consider all the stuff I've bought that isn't relevant to me as a player, but which I own because it's fuel for the campaign I want to run sometime in the indeterminate future, the payoff becomes ridiculous. Core rules and Complete Warrior (ignoring the fact that I really only need the Player's Handbook? $130? 72 cents an hour?
Come on!. I don't even play as much as I used to!
This stuff only feels expensive because it comes out in big hits - but I think part of an intelligent approach to your finances lies in figuring out what you want and how much you're getting out of it. The truth is, I may have spent a truckload more money on my D&D collection than I do on PC games, but I consider the latter more of a waste of my money, given how little I play them, and how restricted they are - I can take my D&D books and read them anywhere.
I think the sensible attitude towards any Fourth Edition is this: It will only be worth it if it makes the game better, the way Third Edition did. There are lots of things I'd like to see that I don't feel belong in a mere sourcebook for a system - a system for handling variation of Level Adjustments for creatures which synergise with different classes in different ways, a streamlining of different kinds of monsters (organisation by type, like the core rules does with dragons, would be a really good idea for undead, and meanwhile devils and demons are collated when they're not even a type unto themselves) - and I would hope that any Fourth Edition would address that and simplify things again the way that Third Edition did.