I believe it should be max cruise airspeed in mph + max gross weight divided by 1000 = pay rate in dollars per hour.

Example for 747:

575+ (910,000÷1000) = $1485.00

Or course that is the captains pay rate and the FO is paid at a percentage based on the max mach # of the captain rate, so in this case I believe it is .84 giving a hourly dollar figure of $1247.40