My expensive "hobby" that is completely dissociated from my academic training (science and legal) is photography. Years and years ago, I even developed my own photographs. Now that was a sidetrack that I abandoned before digital advances in the field made it obsolete. And for the record, I am much more adept with Photoshop than I ever was at developing film. I always get a big kick when I see someone using one of my photos, which they undoubtedly saw on FLICKR. And even more rarely, I get an email or a letter from someone asking me if they can use one of my photos. I always reply in the affirmative and send them back an executed, notarized, no-fee license to use my photo. I have never, and will never, sign a license that someone sends me. Usually, the request is for use of a photo of some well-known object and the requester figures they can use my photo for free. And they are right. In regard to "expensive hobby," unlike virtually everything else in my life, my photography hobby has gotten consistently cheaper with each passing year. The camera on my phone is light-years more advanced than my first fancy camera with multiple lens that I purchased while in the Army in Germany at a music and camera store in Mainz.