Can we get a screenshot of the wine list again? What was the average bottle of wine priced at? Did the list go from $30, $40, $50, $75, $100, $135, $150, $275, $250, $280, $300, $365 and then jumping to $3750?
If so, it is seems very likely the waiter pointed in the general area of a bottle wine and said "thirty seven fifty" If you're a few drinks in, and not wearing reading glasses, I could EASILY see someone not realizing they were pointing to the most expensive bottle and just agreeing thinking it couldn't be more than $200.
IMO. First fault goes to the manager. I'm instructing my wait staff to not ever push a $3k bottle of wine unless its some Sheik(

) rolling up with gold wine goblets and ordering 50 Wagyu steaks. Second fault goes again to the manager for not double checking. It takes two seconds to introduce yourself and say,"it'll be our pleasure to serve you our finest bottle of wine" and slip in the prices somehow BEFORE opening it. COVER YOUR OWN ###. You're not going to offend anyone. It's not like they just ordered an $80 steak and you're asking them if they're okay with the price. This is a freaking MORTGAGE payment.