How would you be sure it was that masterful? From your description it sounds pretty much like a standard sales pitch. It could just as well be that you're simply rationalizing being talked into spending $100 on something you didn't want to buy. You seem to be thinking "He was so good, he even managed to get me to buy this stuff", but the truth may unfortunately just as well be "Gee, I fall for this kind of stuff much more easily than I would have liked/thought".
Doing a postmortem of such a sales-pitch as a target yourself seems to be loaded with subjectivity problems.
I worked as a bartender/server at a corporate restaurant when I was in college. You would be surprised how easily people will do something if you just tell them. Me: Order a margarita. Customer: OK.
And not to get too judgmental, but this is especially true with the stereotypical internet dweller. For some reason Ive come to notice that people of this ilk are less likely to say no for fear of offending/not pleasing someone.
I'd say "OK" too. One of my problems going into a restaurant is I don't know what the restaurant is good at making; I used to make the mistake of ordering stuff the restaurant hasn't made in weeks and it tastes horrible.
If the waiter/waitress was going to recommend me something, its unlikely something the restaurant was especially bad at making, and it would solve part of my problem, and so I'll accept his/her recommendation.
I think this was discussed in Kitchen Confidential in terms of food.