Buyer polls by Purchasing.com have found magnesium selling in a per-pound range of $2.98 to $3.13 over the past three months, close to the $2.95 to $3.10 range being reported by subscription newspaper American Metal Market. Magnesium alloy prices also are under downward pressure, with die casters being quoted for spot prices between $2.45 and $2.95, down from $2.60 to $3.10 late last year.The trade press…