Prices vary from place to place and across the country. Areas with lots of industry will offer more options than a town with only a bar and a gas station.
A refill or swap on a 5# tank may easily cost as much or more than a more standard sized tank.
Swapping one tank costs me X and a handling fee. Swapping two tanks costs me 2X and the same handling fee.
My last, and final, 10# refill cost about $18.00.
Swapping 20# tanks last cost me $24 and change, plus the handling fee. I kept my eye on Craig's list, so I have three industry standard 20# cylinders that cost less total, than my first 10# tank.