For regular, retail customers, Hertz does not charge mileage fees. That only happens for certain flat rate corporate contract codes. Try using the AAA CDP or some other generic one that gives unlimited miles.

Also try picking up and/or returning at a neighborhood store. Sometimes the price is different.

A few years ago I did a weekend roadtrip from SEA to SAN down I-5. But in those days there was a publicly advertised discount called RQ DRIVE, which for one-ways involving a Sat night stay, dropped the price drastically. That's long gone. RQ Drive is sometimes re-appropriated for the FL driveout and other specials, none of which are related to what it used to do.