Well, I can sort of relate to the first part. Pirating for more than a trader can earn isn't very fun, for either person involved. It certainly decreases the chance of the trader actually paying (though there should be roleplaying there, of course - it's amazing how unreliable engines and such can be). The same goes for demanding all cargo for no real rp reason.
Though you shouldn't base whether or not something is fair based on the purchase price as it's the selling price that's important. You paid 300k for it, but how much were you going to *sell* it for?