BktBallRef wroteIt varies from area to area.
Around here, the most common setup is a freshman game at 4:00 p.m., a junior varsity game at 5:30 p.m., and a varsity game at 7:00 p.m. Almost all games are two person games. Varsity officials will just work the one varsity game, always. Subvarsity officials may work a doubleheader, depending on the availability of officials on that particular date, at those times.
No doubleheader "discounts". All varsity game fees are $88.28 for each official. All subvarsity game fees, all the way down to middle school games, are $57.25 for each official. No mileage.