How is covering Festivalsommer 2013 "highly questionable"? Thats a clever way do things!
Getting rights for pictures of artists is a long and messy process, so you best take them yourself and make sure that you are an accredited journalist, so you are actually allowed to publish them. For many german artists, there are no pictures at all. The project has already been tried on one festival last year (Wacken 2012) and they try to cover 30 festivals. Expecting 50 Bands per festival, this potentially yields 1500 pictures (more or less). For that, 18000 is a _steal_, especially expecting that volunteers provide their own equipment.
So, tl;dr: Wikipedia is more than a website, it is also a foundation[1] that tries to improve all aspects of the service in clever ways. This costs money as well.
[1] Actually, more then one, Wikimedia Deutschland e.V. is something completely different. Another thing the Article misses: Wikimedia Deutschland has its own budget.