There is no magic number. It depends on so many variables. Smaller contracts usually go for slightly more. Contracts with lots of banked points go for more than stripped contracts. Certain resorts go for more than others. If Disney decides to start ROFR'ing a particular resort (OKW and BWV seem to be the ones right now) prices are a bit higher. Some Use Years seem to be harder to get. You can also negotiate MF fees and closing costs, so price per point shouldn't be your only concern, total contract price should be.
Study the ROFR threads and find what the resort you are looking at is really selling for. Then determine what total contract price you find acceptable and craft your offer accordingly. I always leave myself some negotiating room by making my initial offer lower in case of a counter offer.