As everyone has said, there's a lot of variables here, which makes it very hard to say from afar. If we knew what speaker was at issue, it would be easier to advise.
That said, I shoot for 60% of MSRP for used gear in good condition (although one can do better on large hard to ship speakers). I recently did this well for a desirable "demo" amp that was as new.
On the wider market, including used, you can get likely find the same item, or a comparably good, or better, item, for $2500 (*lots* of good speaker options in this price category.)
Anything more than 2500, and you are paying extra for the security and support of dealing with a dealer (presuming they provide such support). That's worth something: how much is it worth to you? If it were me, if the price is much over 2500, I'd be inclined to shop carefully, unless it was *exactly* the speaker I wanted, or I really felt good about the dealer.
The real question is, what's the best speaker for you for the money you can spend, not what you've saved over MSRP.