Hah. I run a merc company and I have no idea how much escorts generally snag. Mostly because sitting around looking for escort work is bad business.
Back in the day I'd generally demand about two million, but that was before the advent of the mining mod. Generally my rule of thumb is that I'd ask them to fork over as much as they would if they were being pirated. A cruel irony I'm sure but, at the same time, better to pay the escort than to pay the pirate.
In the GMS/D: or any other mining group that I've put together the rule was a bit simpler: The escorts get paid the same amount as the escortee. Every job was important. Escorts mine. Haulers haul. If there's 5 people the profits get split 5 ways. So GMS escorts generally can expect to make much better money than, say, a trading group escort or a merc.