You can get a wonderful firearm for less than $600. Will it say "Sig" on it? Maybe. You can get a 2022 for $400. Sure you get what you pay for. Sometimes that thing you are paying for is naught but a name and a feeling of misplaced superiority.
The CZ guns are great, and their clones (EAA witness) are often seen under 280 dollars.
(unfortunately, this ad is for a 40 S&W, and my slickguns websight is out of order http://grabagun.com/eaa-tanfoglio-poly-40-s-w-12rd.html