namibia the uranium explorers paradise, page-17

WMEs moving because as U308 price advances lower grade mining operations increase profitability at a faster rate than higher grade operations.

Example
High grade operation $20 to mine pound of U308.
Low grade operation $45 to mine pound of U308.
Each mining 2 million pounds per annum (will exclude overheads , exploration etc).

At U308 price $50, high grade makes $60 million pa, low grade $10 million pa.
At U308 price $100 high grade makes $160 million 167% increase profitability. Low grade makes $110 million 1000% increase in profitability.

So if you are a U308 bull, lower grade deposits/operations are where the leverage lies.