This hobby can be very expensive but everything is relative. I don't think this hobby is nearly as expensive as Salt Water Fishing. Lets see: Boat, trailer, motor, truck to tow boat, mega fishing gear, licenses, taxes, insurance, ramp fees, ice, beer and bait. Trust me, nothing goes down faster in value than a used boat!
One of the big problems with any hobby, this one is no different, and it is with what I call curb appeal. When you participate in audio web sites and you attend G2G's you read or learn about people's perceptions of gear. Those perceptions may be based on facts or totally based on opinions but they definitely have a strong influence on the price of used gear. Another factor, which we are going through right now, is the explosion of the digital age. Digital gear being produced today is simply better and sounds better than the gear made just a short time ago. Thus, the prices of used digital gear drops like that of a used boat.
This is supposed to be a hobby about the music. I think it is more about having a system that plays back music in a manner that you want to hear it. When you are with friends at a G2G you learn that no two people prefer the same type of music or same type of sound. Thank goodness we have lots of gear to satisfy each of our specific needs.
Ken