Keep in mind that one is not "selling" their points, but rather "renting" their points.
When it comes to
DVC, a point is a point is a point...all points are equal. One does not rent points applicable to a specific time period or resort, except when dealing with the 7-11 month reservation period in which your home resort is important, but the value of the point is always the same.
What makes some points worth $9 and others $12 are the intangibles associated with the point...time until they expire, restrictions like the 60 day rule, and when dealing with the 7-11 month window...the home resort.
As a general rule, points at the smaller DVC resorts may command a higher price than the larger DVC resorts simply because of 11 month booking advantage and the popularity of the smaller resorts especially during certain times of the year.