The basses I have that I bought new are basses that were not available used because they were new models---a Gibson Money bass (a Gibson "guitar of the week" that was a very limited run) and a Fender FSR Antigua Jazz Bass. Okay, yes, I'm sure there are other Jazz Basses out there in the Antigua finish, but they are not really Used Instruments, they are Collectibles, which is a whole different market. When Fender did runs of a handful of instruments in Antigua a couple years ago, it seemed like that was about the only opportunity I was likely to have for a while to get one at a reasonable price. Of course, since buying these I have seen them used, but not often---it's not like you could decide you wanted one and find one easily within a short time. [Edit: Antigua Jazz Basses I see for sale presently used are going for about the same price mine cost new; Money basses are going for substantially more than I paid when they were being blown out in 2007.]
I don't know if it counts as buying a new bass, but, I've built a couple parts basses, one of which was made from a new neck and body from Warmoth. Another had a neck I bought new put on a used Fender body. I suppose the dynamics are the same, building a bass from new parts vs. buying a new bass---if I were to sell the necks and/or body I would take the price hit, but inasmuch as I like how the Warmoth necks feel, I don't see any reason that I would ever sell them, and the body was reasonably priced versus buying a quality used body and having it refinished in the color I wanted.
My other basses I got used, and I really can't see buying a new version of something like a Fender P or J, or some other relatively common bass like a T-bird, Stingray, 4003, etc.---except in one circumstance, which relates to another bass I bought new, which my dad is using now but is still "in the family". Almost twenty years ago, I bought a new Fender Precision. I hadn't intended to buy it when I went to the store, but I picked it up and it just spoke to me. It played and sounded great, and it felt like an old friend. If I came across another bass that just had that certain special something, I wouldn't let it get away just because it was new. But that doesn't happen very often, especially since now after years of TB membership I've got a bunch of nice basses and I don't really shop very actively any more.