There should be a slider from between 0-50% of the profits as well as some time based lockout that lets the escort know that there is no possibility of changing the slider to 0 right before the trade is finished. This would allow players themselves to negotiate the terms involved in the value of the escort.
Trader: "Ok shooty-boys, I'll pay you 25% of my profits if you'll escort me to Pew Station in Sector-00-Epsilon
Shooty-boy1: "Make it 50% and you have a deal. Sidewinder fuel is not cheap you know!"
Shooty-boy2: "And I want a ton of gold because, well, just because!"
Trader: <sighs> "Ok, ok boys, it's a deal - just make sure I get there! Deviant Danglers Krew are after me, and won't say I'm a real player unless I trade in Open - so lets to this!"
<completely uneventful trip>
Shooty-boy1: "Ok we are here, I'm going to dock first and keep an eye on the markets to make sure you don't cheat us!"
Trader: "Go on - that's fine."
Shooty-boy2: "And I'm going to sit outside the station to make sure you don't try to run!"
Trader: "Yup that's fine. I'm docking now!"
Shooty-boy1: "We're going to be rich!"
Shooty-boy2: "Yup - I will finally be able to afford a Hauler!"
Trader: <logs off>