Calculating the value of your data is pretty easy actually. Just take the market cap of the company divided by users to get an average.
Google is at about $700B with may ~2B global users, so global average is more like $350/user. The value of US users is probably 10X less developed parts of world (based on ad rates) so US users are worth more like $3000.
You are undervaluing yourself :) which is how they win.
No it's not. You're mixing up the value of the data with the value of your attention. The world has made a killing off of advertising long before personalization came about so saying it's all due to personalization is a bit silly imho.
They would be worth less than zero because without the personal data they would have no ad revenue to subsidize their money losing loss-leader ventures that only exist to collect data and/or suck people in to watch advertising.
The search engine is just a targeting mechanism for ads. You tell Google what you are searching for and they serve you a targeted ad. That has always been the business model.
I personally wouldn't consider search ads with no data being stored or user level history being used as not being personalized or user targeted. They're to me no different from an ad in magazine or a static banner ad on a web page.