That may be true - but again, the amount you buy per cylinder could affect the “cheaper than butane/propane cylinder” issue.

How many “cheap” cylinders does it take to replace one “expensive” cylinder? If three “cheap” cylinders (with, say, 1 ounce of fuel in each cylinders) give you the same cooking power as 1 four-ounce “mixed” cylinder, and the butane cylinders cost $3 each, but the “mixed” cylinder costs $7 - then the “cheap” cylinders really aren’t the better buy.

Generally, fuel with a higher energy content costs more than the same volume of fuel with a lower content (for example, an ounce of alcohol costs less than an ounce of white gas), but the cost for a given amount of energy content could be pretty even (it takes more volume of lower content fuel.)

“Cheap” isn’t always cheaper.