Great question as to the depreciation. My first raft was an 8 year old Down River fully outfitted for $4400. I put about $600 into it and after 6 years and 150 days use I sold it for $3500 in about a day. I think I could have gotten closer to $4k. The rubber is about half the cost, but most of the depreciation from a utility sense. The metal doesn't really degrade. I think buying a relatively new/slightly used raft is the best balance. Some depreciation has already taken place, including not paying tax, and a very long life and good resale. Unfortunately, these are hard to come by. You will never have a boat that is as cheap to own as an old used one, but they surely aren't pretty, but do the same thing with a top off each morning. If you have too much money you will likely buy the newer one.
May the wind be always at your back,
May the sun shine warm upon your face.