Hello ptalk-
The best way to do that in the custom shipping manager would be to assign each product as one pound. Then, for your custom shipping method, you would do the following:
Low High Price Apply Cost To
0 100000 10.00 Each Item in Basket
This will, for each pound in the basket, apply 10.00. So if you have each item to be one pound, then each item will be charged $10.00.