Not necessary, because the author never argues what “should” or “should not” be the case concerning the relationship between wine price and quality. The argument is about what IS the case — does price indicate quality? That’s a different question from whether price SHOULD indicate quality.

Not necessary, becaue the conclusion is just that an expensive wine is “not always” a good wine. The author could agree that price is sometimes or usually indicative of a good wine, as long as it’s not always indicative of a good wine.

Necessary, because if it were not true — if the reputation of a vineyard DOES always indicate the quality of its wines — then the fact reputation can determine price would not constitute a reason to think price doesn’t indicate quality. If reputation always indicates quality, then a higher price due to higher reputation would be accompanied by a higher quality, too. The author must assume this isn’t the case.

Although the author does believe that the reputation of a vineyard plays “a role” in determining price, that doesn’t commit the author to thinking that the reputation plays a GREATER role than the quality of grapes. The author never compares the importance of various features in determining the price of wine; he simply identifies several features that determine price.

Not necessary, because the author isn’t committed to believing that reputation is ever indicative of quality. The author could think that even wines produced be lesser-known vineyards are never priced to accurately reflect the wines quality; this doesn’t undermine the author’s reasoning. Also, it’s not clear if “lesser-known” vineyards have a lower reputation than more well-known vineyards. So the quality of bieng lesser-known or more well known doesn’t have to be related to the concept of reputation.