There are citing a study by the bank "Landesbank BW". You can find the same study in other media mentioned.

A bank is usually very reputable in calculating economics.

Oh, the fear of 'leftist' newspapers.

For the US, pretty much every newspaper in Germany is leftist.

You betcha ;-) Even for european standards this is leftist. They do have good articles though as it is usual for ideologists only on topics where the ideology doesn't already provides the answers.

Also, the mentioned bank is a state bank. Usually not the moste creditable ones. Especially not on issues that include subsidies.