Funny, I buy my propane by the gallon so the size of the tank does not matter, I only pay for what I get put in the tank......
The post referred to pre-filled small cylinders. I use them for dyeing. They used to last 27 hours. They now last around 20 hours. The exchange rate has remained the same, but the price of a new pre-filled tank is up about $15 at Walmart.
I also use propane for home heating/hot water. This year, as usual, I had to call around, get comparative prices and negotiate a price below what my supplier wanted to charge. I got the reduction in price, a snotty service person at the phone center and then, they lowered the amount I can buy under the new price. This will insure that if I need propane after the contract ends, I will pay market. Last year, they tried to charge $4/gallon if anyone needed a fill in April.
I have a replacement provider on tap for next year.