...first of all, mortals aren't supposed to know about any of that, however garbled and incomplete it sounds, and second, if they stumble over a piece of it, you're supposed to shut them down hard and refuse to bargain for their soul of insufficient worth and let them get executed by Cheliax.
But if he's reading her right, she doesn't know. Or she doesn't know numbers.
They wouldn't have summoned him to negotiate if they had even a beginning guess at Sevar's worth; he's not a Count of Hell.
"That is not the way of Hell," he rumbles. "Asmodeus is not Abadar, little mortal, no matter what company you have been keeping of late. You can try to hold what secrets you like, and Hell will keep its own, and whoever is closer to Asmodeus in wit and ways is the one to win the compact. Name to me the price you seek for yourself."