I heat the shop with propane, and use it for the griddle and the smoker, so I have a number of bottles. Six, to be precise. When I get four empties, I load them in the truck and get them filled. $23.99 for a standard 20 lb bottle, and that's about the cheapest around here.
Today, I took four bottles, and the guy who was filling the tanks told me that he had trouble with one of them. It wouldn't accept propane. Go figure, must be something wrong in the valve.
All the Dollar Stores around here have Blue Rhino cages out front, so the next time I go to the Dollar Store, I'll swap that bottle out. Blue Rhino might be a bit more expensive, but they sure make bottle maintenance easy.