In my very short career on discovery just got pirated once: I was mining helium in a 2k freighter and got asked for 1M. If I remember right it was an outcast id but some neutral iff in a bomber... talked the guy down to 700k, still worth more than half my cargo (550 per unit at my point of sale)...
as i was in a 10M ship and had a bit of cash it was ok.
I feel pirates shouldn't ask for more than part of the profit, else they would drive (ipr: the trader out of business or (oorp: the player away from the game.
oh, and pirates should use hostile iff. just like the npc pirates they shouldn't be able to dock everywhere or be spared by npc police/military.