Eh, this was tried on a friend of mine selling his company. He simply said "the deal's off" and walked away. A couple weeks later, he got another call which said "ok" and he got the full price.
> That also puts bootsrapped companies at a severe disadvantage
It's very simple. Just say "no". It's an incredibly powerful tool. It's crucial to getting a proper deal on anything from selling/buying your house, your car, to your company. Be ready to walk away. Sometimes by the time you started your car and are backing out of the parking spot, they'll come running out and say "ok".
But you gotta mean it when you say "no" or you'll fail. They can smell weakness.