One thing to be aware of is that the cheapest place may not be available to you. Many retailers (including REI - search for "fuel canisters") cannot ship canisters to you; the only way to get them is to drive to the nearest retail outlet (to shop inside or use curbside delivery.) And, if you do find a place online that will ship, you'll need to add the shipping charge to the price to compare the cost at your local store.