I love the movie Sound of Music. I've watched it dozens of times. One year for Christmas, my daughters gave me a DVD of SOM to replace my well used VHS. The DVD came with a running commentary by director Robt Wise on the making of the movie. After learning how the movie was made - where the scenes were shot - I would never take one of the tours. Never mind that it is "touristy and hokey". Most of what you visit on the tour are either easily accessible walking around Salzburg on your own (Mirabell Garden, the Residence, the outside of Nonnenberg Abbey) or their part in the movie is pretty contrived.
Leopoldskron was not the Von Trap home in the movie. It doesn't even appear in the movie. The building used as the outside of their home was the Frohnburg, but all of the inside scenes were filmed in Hollywood. The gazebo you would see at Hellbrunn was only used for brief distance shots. All of the singing and dance scenes "in the gazebo" were shot in a sound stage in Hollywood. Did you think that it really just happened to start raining at the end of "You are sixteen"? Nonnenberg Abbey was a kloster when the movie was shot and they were not allowed inside. The interior scenes at Nonnenberg were either sound stage sets (the courtyard) or shot elsewhere (the Chapel). Over half of the movie was filmed in sound stages in Hollywood. Would you pay $50 or more to ride a bus around Hollywood singing "Do, a deer"?
The lakeside patio (where they swamped the rowboat was actually a temporary set copied from the one at Leopoldskron, built on the same lake, next to Leopoldskron.
Some of the tours offer an excursion to the wedding church at Mondsee. That's about the only thing you can't easily see walking around Salzburg, but that's easy to go to on your own. I stopped by Mondsee once on my way through the Salzkammergut to Hallstatt. I also saw St. Gilgen and Wolfgangsee on the same trip.
So, if you think riding around on a bus with other Amercans is worth $50, by all means do it, but don't be fooled about what you are seeing.