I did think of this method - however if a lonely cache (worth lots of points) is suddenly surrounded by a trail of them it will be much less lonely, more often found and its point score will get smaller. Shame for the cachers who found it when it was alone and see their score going down. Of course you could get the points it was worth at the time you found it (which is what my method was trying to do) - Possibly an average over the previous year (or whatever).