About the same as a 6.5Liter 327 Chevy Hemi. What you have described doesn't exist in the real world.
Yes.. offhand, I know of two. Magnum Research made the Desert Eagle available in .357 Magnum, and Coonan Arms manufactured a semi-auto .357 Magnum, based on the M1911 pattern pistols.
50-300
No. 357 SIG and 357 Magnum are two very different cartridges. You can use .38 Special in a .357 magnum gun, but not 357 SIG Adding to the above, the compatibility of .38 Special and .357 Magnum applies only to revolvers. You cannot cycle .38 Special in a magazine fed .357 Magnum lever action or semi automatic.
A .357 Magnum revolver can, as it uses cylinders and does not require headspacing between a cartridge and a chamber. Semi automatic, lever action, etc. .357 Magnum firearms which use a headspaced chamber cannot, however.
300 or so
100-300
50-300 usd
25-175 usd
No - neither a semi-automatic .357 Magnum nor a semi-automatic .357 Sig will. .357 Magnum revolvers can fire .38 Special rounds because 1: they feed from a cylinder which can accommodate the shorter .38 Special round and 2: unlike a firearm with a chamber, the cylinders in a revolver do not need to be headspaced.
Value of a smith and western model 581 357 magnum crome with 6 inch bull barrel
about $600 to $900
100-400