I used to do the same about 15 years ago.

I was living in DC area but was traveling to Bay Area every week (mon to fri) for work.

I always booked fare in reverse with Friday evening departure (from sfo) and Monday morning ( from DCA) return. A Saturday night “stay” apparently made it a leisure fare which was way cheaper than Monday to Friday fare which was way more expensive. (Like 4x more). [ this was United Airlines btw].

My understanding is that this does not work anymore (at least for US domestic). Airfare are all priced for one way (return fare is just the sum of two legs).

However, difference between what business travelers pay and what leisure travelers pay is huge (see hertz rental prices or Marriott hotel prices for saturday vs Monday).