This is such an individual question. Its nice to help out close friends, but at the same time, if you rent your points out at a discount to everyone, what you are essentially doing is helping to finance other people's vacations through your
DVC purchase. If you charge too little, there is definitely the danger, as others have pointed out, in people not realizing how valuable the points really are.
We rented out points to our friends this year. We told them that the going rate for rental was $10, or possibly a bit more, but we offered them the points for $8.50 a point. We thought it was a good deal for us because we avoided hassle and trust issues of dealing with a stranger. We got all of the money upfront. Our friends were happy with the deal, too.
Ultimately, it comes down to what you are comfortable with. IMO, you do NOT owe your friends or family (except probably parents) a significant discount. You paid dearly for the points. But for some people, there is a reciprocity factor (you can use X relative or friend's vacation house ocassionally, so you "rent" your points to them for free or heavily discounted). There are a lot of factors that play into it. But I see nothing wrong with renting to friends for $10 a point. They are still getting an excellent deal and they get the benefit of dealing with YOU rather than a stranger.