Interesting to note that this works out to roughly $700 per employee per month, over a ten month span.
$250M / 10 yrs / 12 months / 3000 employees = $700 per employee-month
$250M / 10 yrs / 12 months / 3000 employees = $700 per employee-month
As Tony Soprano said, "buy real estate cus God ain't making any more". Demand is pretty certain to outstrip supply from here on out.
Your quote would force them to appreciate in price 100 years from now, but on timescales shorter than that I don't see it providing any real guarantee. Just look at Detroit.
Given that the building can be sold for the same price that they paid:
$250M x 2.3% per year (the going rate for one of Google's bonds) /12 months / 3000 employees == $159.72/month
But in total it would be more, because that price won't Cover Runtime expenses
To go even bigger, there's commonly a property tax abatement from local and state governments for large projects and often actual tax credits.