Well, if you're talking about books...then too much
If you're counting DVD's...too much
Close-up stuff....too much
Stage stuff....even more of a too much
And if you're counting sound equipment...too much still.
Just to give you an idea....around 100 books including Greater Magic (2nd edition) and Dai Vernon's Revelations, 50-60 DVDs including a crud-load by L&L (which we all know charges an arm and a leg), enough stage stuff to fill 5 good sized boxes and some shelves, and enough close-up equipment to do the same, and also around 150 decks of cards and counting.
I'd kill myself if I ever knew the real amount I spent though...
~David Rysin