That is reasonable. I see mk 4 and mk 5 units closer to $4200 often. Mk 6 is usually a bit higher. It is not a deal at $5, but not crazy.
I do want to call out here that the mc275 does not handle.complex impedence curves well. I have one I used on my NX-tremes and it was *bad*. I switched to Van Alstine 225s and they are doing much better.