tghe P-40 is no longer made, but i think the only difference between that and the p-11 was.. a difference (not exactly sure) in the mag, and barrel obviously. They are (in the right groups) a sought for weapon, but i have heard (havent shot) that they are really snappy. I know some feel the P-11 is snappy (9mm) so i would assume the same platform with a hotter round would be more so.
I love my p-11, and if i was looking at the .40S&W round, would love a barrel etc for it. But have too many claibers as it is now. But, the P-40, then maybe a 9mm barrel and mags......
The price seems to be about what i would expect for gun, mag (or 2) in goodshape. They seem to be going for about that for full gun or conversion kits on another location.
Good luck and let us know.