Restaurants are expected to charge a 300% mark up on wine, so in reality it was only about a £1000 bottle of wine.
It's going to be corporate entertainment, if you're pitching for a multi-million pound deal, getting the other side hammered on booze costing a couple of thousand is a bargain.
At least European wine is fun, it's a memory game based on rivers, and trying to remember what area grows what grape, and everyone finally admits they don't know anything. US wine takes itself far too seriously and is scarily expensive.