As someone who is in the process of moving right now, I sympathize with what you said. However, I disagree. the "just compensation" should be whatever the property's fair market value is.
The market value of a piece of property is whatever the highest bidder will pay. Owners of property which is being siezed believe the property is worth more than what's being offered. Their valuation is the correct one.
So they should just be able to name their price? Methinks there might be some price inflation if that were the case.