I noticed the same on GB, which is how I scored a very near mint USP40 V1 with 5 magazines for $419 shipped, which seems like a hell of a deal even among the softer values found for .40 S&W. There has been a USP40C listed on GB for some time for $425+ shipping with one mag, which wasn't quite good enough to pique my interest.
Similarly, and the thing that started this whole game with HK pistols all over again, was considering a change for my daily carry and I stumbled on the late Todd G's 50,000 round test on the HK45. Which resulted in me buying an HK45C LEM shortly thereafter.
Hey, a sample size of one is still data! I'm glad to hear it runs well with the 9mm mags and recoil spring. Does it regulate to the existing sights well? And how was the wait time from EFK? About as they claimed? (60-90 days)
Thank you for chiming in!