http://www.bbc.co.uk/news/uk-england-devon-27763664However, in 2005 Ernst van de Wetering, one of the experts who questioned its authenticity 46 years ago, concluded the painting could be genuine.
30million is a lot for something that 'could' be genuine.
I think it is something of an authenticity bubble...
Lots of people in the present and past have been good enough painters, and these people often have students who paint in a similar way, at the similar time, with similar paint etc.