What is the most expensive Bitcoin purchase ever made? Relying only on publicly disclosed data, what is the most expensive Bitcoin purchase that has ever occurred?

"Expensive" can be determined either by:


Highest purchase price in Bitcoins
Highest fiat value equivalent at the time
If you mean the greatest amount of bitcoin spent,  the "bitcoin pizza" comes to mind. At a whopping 10k BTC spent.

Pizza for bitcoins? (bitcointalk.org)