I've never really bought anything that I worried one iota about what I could sell it for... I guess it is because I just don't buy that much stuff. I only buy if I really, really want it. or if it is Really , really cheap or at least a good price. I like the familiarity of things I am comfortable with.
Of the 9 guitars I have bought I still have 6 of them. I have bought a few pedals recently but all were on sale and almost all not expensive.
I am just a hobbyist musician so this is not a money decision, it is a do I want it decision.
I will have to figure out if I want to sell anything soon. My kids don't play so I have to get rid of the few things I have.
Nothing I have is unique. 83 cruise, 84 Proto II, 84 Blitz bass and some imports.
Maybe the Ibanez Phaser Tone II from the early 80's? Not really a sound of the modern Guitar player though.