for what it's worth, i had about a 50% success rate in college at meeting with a professor after my final grade was handed out and asking (with some form of justification) for a higher grade.
professors would get very squeamish and often bump my grade up (from a B to an A-, for example) on the spot.
I'm aware, but I'm trying to take it one step at a time for those just starting out. I've trained a few people (mostly friends and family). A common thread among people who don't negotiate is a belief in fairness. That haggling is about asking for more than what the other person thinks is 'fair' (hurting someone). I've never once had success teaching people that words like 'deserve' and 'fair' have nothing to do with pricing a transaction.
So I divide it into two sides: negotiating to get more that what you 'deserve' (which they can categorize as unfair/wrong/evil etc..) and negotiating to get exactly what you deserve. They start out believing that all negotiation is the first type. Introducing the second type makes it easier to rationalize negotiating for what they deserve, and that it's not 'that other unfair type of negotiating'.
professors would get very squeamish and often bump my grade up (from a B to an A-, for example) on the spot.