Airline tickets are cheapest between midnight and 2 am on Wednesday morning (as in Tuesday night into Wednesday morning). The pricing wars peak around this time, so that's when you'll want to get them.
Don't go through a travel site. They're not going to give you the best deal. They're like ticketmaster and charge a conveniency fee. The thing I always do is use a travel site when I want to buy the tickets and then go call the airline. They'll give you the best deal.
2 billion dollars...sir, I'd handle my grandpa's balls for 2 billion dollars.