You can't. $5,000 actually is not that bad, I've seen much higher.
Unless you want to attempt to travel through the Drake Passage on your own boat, which I wouldn't recommend. :)
There's a reason it's so expensive to get there and that's also part of the reason it's relatively untouched by tourism.
Your best bet is probably checking ticket prices close to departure date to see if they've budged on the price at all.