I have a couple of 'regrets', but looking back, I made the right decisions...a 1940s Slingerland 6 string banjo...sold to a friend's brother, stumbled on it again several years later at Norman's at twice what I had sold it for, but I wasn't using it, and had not touched it for years....and it paid for part of one of my kids' braces. My Rickenbacker 320 [yes, sometimes owners sell them despite the article's claim]...I was no longer doing Beatles and Byrds material, and it really wasn't getting played...paid for my alimony/Child Support one month. A '63 Fender XII...that guitar paid for itself in rentals to other guitarists....but I needed a Marshall halfstack....which was eventually stolen. My second Marshall SL100/1960A halfstack...sold to pay for baby furniture.
Now truth be told, I toy with the idea of thinning my herd periodically. The cases don't all fit in the closet anymore, and there are guitars all over the house, electrics, acoustics, a/e's, basses, lap steels, ukeleles, violin, koto...and I would like to get another 12 string [and I don't know why!]
What would I let go? Hmmmm...my early 70s SG, my 2002 ES135LE, the Robelli resonator...and then there are all the amps...and the pedals...and the keyboards... and...