Switch to a "one book" game, and drop down to: rulebook, character sheets, notepad, dice, pencils? Better still, drop down to a game where all the rulebooks exist in electronic format, load them onto an iPad or similar, and consolidate with the notes. And then if you're willing to go with an electonic dice roller...
However, assuming you're sticking with D&D, I think your options are actually fairly limited. You should be able to safely get rid of the external monitor, and maybe the speakers. Also, you should be able to downsize the laptop itself. Oh, and that electronic dice roller removes the need for physical dice at the table.
Beyond that, I don't see many possible savings. Your biggest remaining overhead would seem to be the minis, but 4e really loses something without at least some way to track exact positions, so...