FedEx CC pays not by the mile but a percentage of the load. To determine your per/mile rate, you divide the miles driven by the dollar amount paid. Ballpark for us in a straight truck ranges from $1.00 to $2.00 a mile, sometimes higher, sometimes lower.
Some expediting companies pay a set per/mile rate. $1.25 per loaded mile (or thereabouts) is common. Those are rates for stright trucks. Tractor/trailer rigs can earn more.
When you hear of loads that pay in the $2.00/mile plus range, there are often accessorial charges added in like extra charges for reefer freight, extra charges for labor (loading or unloading the truck), and extra charges for delivering freight not just to a loading dock but perhaps using a lift gate to get it on or off the truck or a hand truck or dollies to get the freight from your truck up to a 20th floor office.
If you are coming from a line-haul background, note the important difference in the miles mentality found among successful expediters. A whole bunch of OTR big rig drivers have entered expediting only to leave it soon after because they could not adapt to the irregular way expedited freight moves (and does not move!). Among those that were able to adapt, many consider it the best career move of their lives.
I know a driver that went from a long-time career as a big-rig owner/operator to a B-unit (Sprinter van). You couldn't pry him out of that van with a crow bar! When asked about the differences between the two kinds of driving, easy U-turns is one of the first things he mentions.