Buy one song, and you get another one instead for the same price. Or none - for the same price.

Apple's customer support is often ghastly. In June 2012 I reported to them that several tracks of this recording were empty: https://itunes.apple.com/fr/album/bach-matthaus-passion-bwv/id309852339 

Check for example tracks 14, 15, 24, 25 and others. Apple reimbursed me. (Thanks!) But they still have not removed the broken recording, and they still sell it to other people. After 18 months! The tracks are empty. There is not even 4′33″ of silence. There is 0'0" of nothing. But Apple charges 0.99€ for each of them.

I thought that was an isolated case, but I recently bought Beethoven's complete string quartets: https://itunes.apple.com/fr/album/beethoven-complete-string/id152213181?l=enhttps://itunes.apple.com/fr/album/beethoven-complete-string/id152213181?l=en

It turns out that the 15th string quartet has cembalo and a singer. It seems to be Vivaldi: Juditha Triumphans, R.644/Pars Altera-"Haec in Crastinum Serva" with Vittorio Negri & Berlin Chamber Orchestra & Birgit Finnlä & Julia Hamari. Click on the preview buttons to hear it.

Not Beethoven. Not a string quartet. But Apple charges you for it.

Can't they afford to check what they sell?

Tracks 14 and 15 in this screen shot are 0.00 seconds. 

Bonus exercise: calculate the price per minute.