The most expenive shells with the Hevi-shot are probably the turkey loads. The lighter duck loads should be less money. You could also consider having a gunsmith shorten the barrel a little, which would reduce the choke, and you could then use steel shot, which is the most economical way to go. Back when I hunted ducks a lot, I almost always had my improved cylinder choke tube screwed in, and I used #2 or #3 steel shot. You'd be amazed at the tight patterns you get with steel shot using with an improved cylinder choke. Killing ducks up to 40 yards is not a problem. Personally I would never use shells for duck hunting that cost more than 50 cents/shell, which would be $12.50/box, and actually I think prices have come down so that now you can buy a good box of steel shot shells at Wal Mart for $8 a box. Hevi-shot would be great for goose hunting but a waste of money for ducks, in my opinion. But it's an option if you want to use that old Ithaca model 37 without altering the choke.
