I think $2500-3000 is more realistic for a break even point:
$1050 booth fee
$575+taxes ($115/night cheapest hotel on their list 8 miles from convention, 5 nights)
$335 airfare (I just did a Delta price check for a random Tuesday-Monday in Feb Burlington Vt to Chicago area to get an idea)
That's $1960 plus whatever the tax on the hotel room is, and you still have to get from the airport to your hotel, and hotel back to airport, eat/drink, get the 8 miles to and from the convention center each day, get your cards there and back home, and you haven't allotted anything for buying. That's not counting what it costs to buy cards to sell in those $3 or half price boxes.
Don't forget, you'll have hundreds of competitors on the show floor, and everyone buying knows that, so you can rest assured anyone picking out more than one or two cards is going to ask you for a better deal than the $3 per or half price. The other problem is keeping your eyes on the boxes at all times. With just you there, the potential for walk offs increases, especially since you have to be set up open-close each day. You're making a sale and have 4-5 other people browsing, stuff can happen.