Information on wine tasting

[fioribianchi]

I live in Italy. I have some friends coming over from the States who would like me to take them wine tasting.
I took some people last year also from the States and they were shocked by the cost even though the two wines tasted were excellent. They paid for the two bottles they had consumed but didn't buy anything else.
I thought that wine tasting was free and then one usually bought at least a bottle or two even just to be polite.
Please someone give me an idea of the procedure so that I can tell my friends in advance what to expect.