Why are .40 caliber handguns so cheap?

Factual Questions
1

While doing a little surfing for handguns, it seems to me that .40 calibers are substantially cheaper than everything else. e.g., I saw a S&W 686, like i had in the 90s, is going for something like 6-7 hundred, while the particular SW model .40, automatic, is going for something like $325, mol. In the 90s, the 40 was considered a super new gun, and I think that the new prices for the same gun.s were reversed. Why is this the case? Also, when I went to Wally World, i noticed no lack of .40 ammo, while, of course, the others were nonexistent. Comments?

Thanks,
hh

2

From what I’ve seen, new 40SW and 9mm of the same model are very close in price, usually with 40SW being slightly more expensive. Keeping with the S&W - the Sigmas in 9mm and 40SW are all around $350-$370