Yeah this is basically my take as well.

The problem with not having eminent domain is that without it, for any project of sufficient size you'll end up with ~100+ land owners who each individually have veto power over the entire project. If 99 of them freely agree to sell, but 1 is really stubborn and refuses to sell at any price, the project is dead.

There's also a prisoner's dilemma problem. Maybe it's not a big deal paying one stubborn guy 100x fair market value for his property to allow the project to continue. But if enough people think they can get 100x what their property is worth if they just hold out a bit longer, that also kills the project.

Eminent domain solves all this by making it so the project only has to to clear a few bars the government has set for it, rather than the many bars ~100 individual landowners set for it. But in the process it also erodes property rights and kills the built-in protections the free market has to ensure such transactions are fair.

A 1.5x or 2x multiplier on the fair market value would help with that a lot and help ensure eminent domain is only used in cases where it's strictly needed.

Or alternately, I sort of like the idea of letting the landowners elect someone to represent them in negotiations with the project developer, and then having a chance to vote yes/no on the final cash offer. Then the final price would still be set by a market of sorts, but there'd be no prisoner's dilemma or individual spoilers. Not 100% sure if that would work better or not though; it is a bit more complicated and there are still some issues with it.