Having had a night to think on this...

It sounds like CA needs some eminent domain reform. I don't live there, so I don't know (and don't are to look up) the law. In the US in general the constitution requires a fair price, if someone bought land we have evidence of the fair price. My general advice (though often not allowed by law) is that you should pay 10% more than fair if they sell now, but if they go to court we only pay fair price (thus if you disagree with the fair price by 5% you should sell now anyway)