I really am not sure what the most I've paid for a specific bass is. I started playing in 1978, so I've owned a lot...buying, trading, selling...
I know in the 1990s when my GAS reached its zenith I bought a few basses in the $1000-$2000 range including MMs and MIA Fenders and some other things.
Before that, in the early 80s, I bought several pre-CBS Fenders--guitars and basses both--all for well under $1000. Best deal I ever got was probably a 1962 Jazz bass for $350 with original case. Somebody had painted it (badly) with what looked like yellow house paint applied with a big brush. Later I learned to refinish instruments, but I was only 14 or so when I got this Fender Jazz and my dad helped me find a guy who did a beautiful pro refinish on it.
Anyways, these days my most expensive bass is probably my old headstock SX 57P bass, which is currently disassembled for imminent surgery. Cost me around $130 shipped in 2006. But I am upgrading some parts (it survived a flood and needs all new electronics for one thing.)
I also have an old 70s MIJ Lotus P copy--bone stock as far as I know--that I picked up last year for $125 total.
Most recent acquisition is an older Squier P bass. I was in a pawn shop trying out an amp and I ended up putting the amp in layaway, but I had them bundle the bass into the deal. I grabbed the Squier bass just to try out the amp but it felt and sounded sweet enough I just didn't want to leave it there to be neglected and gather dust. All told, it'll end up costing me about $40. But I am going to install a new wiring harness and probably replace the pickup. The pots are cheap and scratchy and the jack is messed up.
So, as far as basses themselves, I (sort of) have three with a total investment of $295, then I'll probably wind up throwing another $100 maybe in parts, not including new strings. I'll do the mods and setups myself.
I'm thinking for under $500 I will have three perfectly functional, nice feeling, nice playing, nice sounding workhorse basses.
Nothing at all against people with massive collections and who choose to buy high end boutique instruments. That's great! I love hearing about those, NBDs and big family pics. Nothing like a new bass!
But for me, I'm going minimal. Might very well not even keep all three basses I'll end up with, but right now only one of the two I have works and the third will be in layaway for a few weeks.
I don't know if I'll ever buy another bass, actually (more likely pedals, amp stuff, etc.) but if I do I see no reason whatsoever (for me and my needs) to ever pay more than $400 for a bass, as long as I can try it out before I buy it and it is as decent as what I've got now.