I struggle with this issue a lot.
I used to be a "one bass to rule them all" kind of guy, I found myself wanting to be able to play fretted and fretless, so I ended up with 2 basses. then, in the pursuit of different tones and variety, I slowly added different basses.
Most are inexpensive, but good players, and now, I flip back and forth about the balance between the value that bass gives me by giving variety vs the small amount of money I'd get back from selling it.
I suppose there's the philosophy of being a minimalist that appeals to bassists in general that drives me to want to downsize, but when I think about selling off one of the herd, I play it for a while and I realize that there indeed was a reason that I purchased that bass in the first place.
It's different as I've gotten older too. when I was younger, I was short on cash, so I really could only have one nice fretted bass and beater fretless. Now, I have more extra cash, so having extra basses around isn't such a big deal, especially if they're not so expensive.
The problem is, I've got 12 now. It seems ridiculous. I basically play 3 or 4 at the most, and the others are part of a sonic palette in my head that really only gets used for recording, since live, really very few can tell the difference between basses IMHO.
It gets even more complicated for me when I hear the sound samples that people post here on TB comparing the Pbass tone with a Jbass neck pickup soloed, and it's indeed difficult to discern a major difference, and this is soloed with headphones! In a band contect, I suspect a small minority of us could really tell the difference.
I just made a list of the basses I own. Maybe some of you can help me decide which one(s) to sell...
1. Fender Heartfield DR5. This is the save-from-a-house-fire bass.
2. Fender MIM Jazz 5. Great neck, passive Jazz tones for days.
3. Brice V2 5 string fretless. No lines. Bought it to work on fretless, great tone, great player, no resale value.
4. OLP Tony Levin Signature bass. Cheap stand in for a Stingray 5. Love the tones. Strung with Chromes right now. Strings are a little close together though.
5. Fender MIJ '75 Reissue Jazz. The number 1 4 string for me. Love it, tone, neck, blocks, binding. Awesome
6. FrankenFender/Squire. Parts bass that I love. tobacco suburst with Squier VM Jazz neck and '62 reissue pickups and Gotoh brodge. Made it to look just like the Kent Jazz bass I started with back in '82. Also has Chromes on it.
7. FrankenFender Jazz. this one is redundant but I had the body from the Squier VM Jazz, and found a nice MIM Jazz neck for cheap. Maybe this one I should sell.
8. Squier VM Jazz Fretless bass. Jaco clone for cheap. Plays and sounds better than it deserves to. I got this when I realized that I needed the fretlines for fretless... :-/
9.Fender MIM Pbass with Mighty Mite neck. Regular Pbass, black with rosewood board, black pickguard, black knobs. Simple and kinda cool. Got it for cheap, thought everyone needed a Pbass.
10. Ibanez RKB900. Awesome passive bass. SD quarter pounders, Badass II, Hipshot tuners. Great PJ bass.
11. Ibanez ATK300. Older one from 1990. Phenomenal neck and tone. This used to be my #1 4 string.
12. Fender Sting signature bass. Single coil pbass. Don't mind the Stinglay. Sounds suprisingly different from a regular Pbass. Records really well.
I feel like I have a problem or addiction...