Personally I base my demands on a whole bunch of factors. Chiefly would be my current mood. Then after that, their level/cargosize, ship/IFF/ID, and their attitude. If I don't like how things are adding up, I can go up to 2 million, but mostly I just based off the RP of the trader. However, if their RP is excellent and they're Synth Foods, they're still going to have a bad time.
The only times I've had people refuse to payout is idiotic OORP types, who I feel no remorse for.
