Registration is $75 this year. I'm not sure about hotel costs. If I was just taking a stab in the dark, I would say maybe... $120/night? I can't remember what the costs were the last couple years, so that's totally just a guess. You can reduce your hotel costs by finding people to room with if you'd like.
After that it's mostly food, and that's entirely up to you. The hotels have little kitchenettes, so you can choose to do a little shopping and eat at the hotel, which is cheaper than going out. The hotel offers breakfast every morning, so it's just lunch and dinner you need to think about.
If you're from VA, you can probably drive up for much cheaper than it would cost to fly, if driving is an option for you. There's a thread on FetLife (and there might be one here, too) where you can post looking for someone to ride with to reduce that cost as well.
Sorry that no one has been able to really be more specific, but a lot of the cost depends on choices that you make.
I would say that if you decide to stay three nights (Friday - Monday), and ate lunch and dinner out Friday, Saturday and Sunday and spent about $15/meal on average, you'd be looking at somewhere around $500 for the whole thing, plus travel costs, which I have no idea about. But again, this is a super rough estimate. If you buy some food to keep in your hotel room, your food cost will be way less. And if you find a roommate, that cost will go down as well.
Lastly, NEST has some volunteer spaces open that can help reduce the cost if you're interested and there are still spaces left. Get in touch with Lee for that.
Good luck! Hope you can make it!