1) Welcome to FT!

2) Three seats together, to Europe, in the summer, at 3 months' notice, is an insane unreasonable expectation. If you can maybe travel on different flights, try Virgin Atlantic. They have availability in July.

3) Your profile doesn't say where you are, so I'm gonna assume you're in Charleston, South Carolina. Tickets from CHS to London are pricing out at $1,000 per passenger. Maybe that's what you meant by $3000 above, but that's really not that bad for Europe in the summer... and it's an L fare so I don't expect there's much lower.

Personally, I'd buy the tickets, and do so sooner than later, or else that L fare's not gonna be available. More seats will likely not open up for coach to Europe in July, unless you really want to risk it and wait until a day or two before. Even then, you might be stuck with TXL or IST or something.