Blackmail? Extortion? Powerful words.
All because of a clause in a contract. You are some naive folks. If one puts down serious coin on a purchase that is dependent on certain economic assumptions for a successful outcome, you should have clauses in your contract to back out if you need to. If you don't you are assuming more risk than you should. Read--not being as smart as you could be.
Jealousy is such an ugly emotion.