If a Jeff Bezos announces he'd be buying property at irrational prices in your neighborhood just as you are reporting your taxes and then changes his mind afterwards should your tax returns be affected by some oligarch's whims?

The value of anything is nothing more than an opinion. A sale is a temporary agreement of 2 opinions. The "market price" is someone's estimation of prevailing opinion. As the good book says, prevailing opinion can change from "hosanna" to "crucify him" in the span of 2 weeks.

Why shouldn't inland revenue have it's own opinion on prices?