It depends on which model and whether it is new or used.
Sig Sauer P229 chambered in .40 is pretty good
Yes, you can fire a .357 Sig round (not a .357 Magnum) in it, but you must first change out the .40 barrel for the .357 barrel.
No
both good
P239
Glock 31 .357 sig pistol is the current sidearm of the NJ State Police.
100-800 USD or so
$200
Supply and demand
Maximum range of a .40 cal pistol is about 960 meters. ACCURATE range is about 50 meters.
100-400 USD
Sig Sauer P229 and P239 chambered in .40 S&W. Here's the press release from Sig.