Though another reviewer touched on this subject, I can honestly say that this whole wine tasting fee baloney takes the edge off of a once exciting Napa visit where you can taste wine, and you are served enough to make a decision when you have to consider spending $30 to a couple of hundred bucks for a bottle.
Sure, slamming may have been part of the rationale to start the fee, but fact of the matter is that most of the wineries take that money as additional revenue, and do not give it back by applying it to a purchase. What I have been told is that the Napa legislative body instituted that ordinance on the premise that it would prevent accidents from drunk drivers overdoing it at the wineries. If they had to pay, they wouldn't drink as much. But this gave an excuse for wineries to glean more revenue from visitors, and frankly that's a turn off and not really in the spirit of the law.
Meanwhile, they serve you a small puddle of wine in the tasting and expect you to make up your mind instantly to purchase an expensive regular or reserve bottle.
Some of the wineries do give you credit if you purchase, and in my opinion that should be the standard in all wineries. You might have to pay $20 for a tasting, but what they give you is much less than a traditional pour at a restaurant, hence the "ripoff."
Like many other attractions around the country there has been a turn to profits and revenue rather than to lure the customers into enjoying their experience. Consider, for example, Las Vegas where getting people to gamble was enough as they poured on you perks, great hotel rooms at low prices, etc. Not so anymore as costs there could be as much as visiting New York.
Similarly, Napa and Sonoma did the same thing by their comp tasting, but now it's also big business there, and I guess the wineries don't want to lose a penny from a drop of their wine. It's a shame, and that golden era of tourism in wine country is apparently now long gone.