Of course, ink also costs...
D&D is one of the more expensive games on the market. As some have already pointed out, while people who merely want to play can get by with the Player's Handbook, Dungeon Masters need all three books. At retail, that's $90!
And that's before you decide to get a setting book, which costs another 30-40.
Most RPGs aren't that expensive, with most buy-in rates around $40-60 for one or two books. (a few months ago, I would have said around $30-45, but some of the main game companies have switched to a two-book format or one-very-big-but-expensive book for games.)
Now, that said, roleplaying is only as expensive as you make it. Once you have your core rulebooks (in your case D&D - I started with the $30 copy of Vampire) you can run forever on it. If you want more information on a setting or system, that's when you buy the *optional* stuff that it gets expensive. Still, you'll be able to run games for quite a while with just the SRD - all of which is free for download.
Coming to Enworld was a good move - if you feel frustrated with the game - there's already tons of people here who have had the exact same problem you've had and can suggest how to fix it. I know that they've helped more than a bit - I'm familiar with roleplaying in general and familiar with many different systems, but I didn't get into D&D3e until recently.