Are there any that don’t cost an arm and a let now?
I’m asking for friends who are visiting for the first time. It seems that everyplace that I’m familiar with now charges between $75 and $150 per person to visit. That, sadly, turns Napa into a very costly venture.
If your friends would consider Sonoma, take a look at the pinned Sonoma travel thread -
Someone also posted somewhere last fall that wineries are being restricted on the number of tastings they can do daily, which drives up prices.
I’m in the same boat planning for a trip next month and find myself getting very choosy about where we plan to visit and reading recent reviews to see what people are saying.
Head to Santa Barbara/Lompoc or Paso Robles. Can still visit and buy wine there without raiding your kids’ college fund 
There are a bunch that don’t cost that much and wave fees when a couple of bottles are purchased. One of my favorite wineries in Napa is Hendry. They make great wines and their prices are very low for the quality of wine. Also one of the best tours and tastings in the valley.
How into wine are your friends? Do they have a particular varietal they enjoy?
Envy Wines and Peju are also very approachable (price-wise).
They like wines but they’re not geeks. They prefer Pinots and white wines but drink a fairly broad variety.
Then they should definitely go to Sonoma instead of Napa.