sub-$400 price range semi auto pistol...
In the market for a decent semi auto around $400.00, I would look into a major brand, used(like new or good condition) law enforcement trade in.
Sites like JG Sales, GunsAmerica.com, Cheaperthandirt.com, Gilbert's Guns, Buds etc have good prices & choices.
A used SIG Sauer P6/P225 9x19mm, a Beretta 92 or 96 pistol, a 3rd gen S&W like a 4546 .45acp or a 5946 9x19mm, a Walther P99 in .40 or 9mm, a Glock 23 or 22.
A used SIG P229 .40 or a Glock 22/23 are a smart pick IMO because you can switch out the barrels from .40S&W to .357sig.
With some major pistol models you could also buy a .22LR kit for cheap, low recoil(less wear & tear) skill training. These add-ons run about $200-300.00.
If you are inclined you can also buy new springs, magazines, sights, grips, barrels. Parts & service work are a lot faster & easy to replace than a DA revolver.
There are a few $400 range NIB pistols out there but quality and service life may vary.
Clyde