This is the mistake I saw so many people making when I was selling gear. Yes, you might have paid a lot of money for something when it was new, but that means nothing in terms of what it will realistically be worth to a buyer used, years later. Everyone thought their expensive, old stuff was worth far more than it really was. Technology changes rapidly, and no one wants big heavy cabinets anymore.
I recently took several pieces to GC and I knew what they would realistically sell for because I looked them up on the used market. One was a fairly desirable SWR cabinet that I had tried to sell online, but no takers. They offered me exactly what I expected to get, and their offer was fair. What did I accomplish? I cleared out a massive amount of needed floor space and put some dollars in my pocket that I didn't have earlier. Gear is NOT an investment. Sometimes you get lucky and things become desirable enough that they hold value, but the majority of stuff you buy will eventually become obsolete. That's just the way it works.