It's a little of all these answers. I plunged $37k into a hobby because I enjoy tech and seeing what the different lenses or bodies do better. I started it as an ice breaker to meet girls at fetish balls, but when I got married, I got more serious. My parents died of cancer andleft me a lot of $$. They were into photography when they first met, though film was too complicated for me at that time.
I was bought a 7d by my fiancee as an engagement present. My sister shoots Nikon, but Canon seamed easier to understand and 7d was my 1st love. 8fps! Now, I have a 1DX. And it's mostly for adoration from friends. My wife cannot play pool to save her life, which was my last obsession.
I would have zero problem selling many of my lenses or bodies if and when I need to. In the meantime I get to capture my life to relive at a later time. One day I may make money off of it, but I wouldn't know what to charge. Besides, there are more to learn out there.