Dale,
You're right, the little bottles are very expensive when compared to buying "in bulk" with the larger tanks!
On the trailer where I mounted the 1# bottle under the galley, I first installed a 5# tank on the tongue, but then decided that it didn't look very good there, was way too close to the open front window, and there was a lot of plumbing to do to get the gas to the stove.
For me, the economy wasn't a big enough issue.
We used a bottle or two per camping trip a couple times a year.
We spent way more on "special" camping food and ice, and gasoline, etc.
Now that we have a bigger camper with water heater, furnace, and stove, a bigger 11# bottle makes more sense, not so much because of economy, but because I don't like to run out, which is why I installed the tap in the system for a 1# bottle.
It has come in very handy three times in the last 7 years.
We could have used a 20# bottle, but the physical size made it a bad choice (too much hitch weight, and just looked out of place).
Rob
Waiting for "someday" will leave you on your deathbed wondering why you didn't just rearrange your priorities and enjoy the time you had, instead of waiting for a "better" time to come along...