I honestly don't understand people defending such vague and irresponsible behavior by the restaurant. The fact that they made no effort to ensure payment was possible before allowing their $3800 product to be consumed makes me think that they had an inkling that they didn't know what they were getting into. I mean, if they did make such an effort, it would have tipped off the guys to how much the stuff cost. No matter how you look at it, they weren't clear at communicating the price of their product and allowed it to be consumed. Therefore, they forfeit the difference.
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You're wrong, it is exactly the the job of the waitress to ensure that the price is understood when the price is asked, which it was. For god's sake he said he didn't know anything about wine, the fact that they would recommend one of the most expensive wines to somebody who obviously can't even appreciate it (assuming we believe that the difference can be tasted) is woefully negligent to the point of suspicious.