Also, each owner is different. An owner who needs the full amount listed to pay off a loan might not be up for much of a discount. An owner who already has priced his contract at a low and fair price might wait for an offer that is at list. An owner who doesn't have a loan and just wants to get the sale done with might entertain a truly lowball offer.
Generally, the larger the contract the harder it is to sell, while contracts of less than 100 points move quickly. I wouldn't expect someone selling a 25 point contract to negotiate at all, but someone selling a 500 point contract might sell right at the ROFR line.