50% always seems so antiseptic to me. Granted, I realize it is for ease of play. I often use 25% + 1d4x10% as a starting value, and then allow my PCs to haggle to improve the price (using Diplomacy/Bluff/Intimidate, based on the situation). It takes a little more work, but my players seem to like it. It isn't by the rules, though.
50% always seems so antiseptic to me. Granted, I realize it is for ease of play. I often use 25% + 1d4x10% as a starting value, and then allow my PCs to haggle to improve the price (using Diplomacy/Bluff/Intimidate, based on the situation). It takes a little more work, but my players seem to like it. It isn't by the rules, though.