How does an LP tank exchange compare to a straight refill in $?

[Acer]

So, what's the premium on exchanging your tank, e.g., Blue Rhino, at a Home Depot, et al. compare cost-wise to refilling a tank? In these parts, a refill requires a special trip to a small distributor with inconvenient hours, so there is some convenience factor. I wonder what I'm paying for the convenience.