Should land -- a scare, limited resource -- be a private or public asset? I believe you're coming at this from the former perspective. But, it's worthwhile to ask this question so that we can understand why it could make sense to give the public a say in how land is allocated and used.
Also, I'd like to point out that when you say:
> I tend to lean lefty, but this scheme makes me understand why libertarians want less government
It's quite easy to replace `government` with `a large private company` in your hypothetical:
> If ~government~ a large private company is counter offering all of my neighbors and they are accepting it, then I am screwed. I either accept the ~government~ large private company's counter offer or ~I go to tribunal who will cite all of the government's recent purchases from my neighbors to set the price at something very close to that anyways~
With, of course, the downside that there's no system-level recourse when the large private company uses its power to either:
- undercut your "market value" of your home and force you to sell
- or make living in your home terrible due to it successfully buying up and controlling all of the land _surrounding_ your home
Both lead to what you are saying you don't like -- some _external_ actor coming in and controlling "how much [your] home is worth."