If you start a request that doesn't get filled and decide, what the heck, I'm going to drop the cash for it and fill it myself. Do you give up the points that other people offered, because that's kind of cheating?
Chapter Hawk, good etiquette should be that you edit your request post to let everyone know you no longer are seeking the item. If you don't, and then someone comes along a fills that request, problems will arise if you say you don't need it anymore. Whether or not you decide to share it with others who offered points is up to you, but you should ;o). And they should give you the points they offered.