Bottled gas. We use the Gaslight, lightweight plastic gas cylinders, in the caravan. I keep two, one in use, one ready for when we run out. Last time out, last week, we set off with a just a drop in one, and a good bit more in the second one, the intention to drain the bit, so we could sort another full bottle.
When I first bought into the Gaslight, the refills, I could get for a very reasonable <£20, from a seller not too far away, when others were wanting £36 for them. That seller was jumped on, from a great height, by the company, for undercutting others. Since when the price of a refill, has gone up, and up.
Looking for a refill today, they are wanting £60+ at many places, some as high as £80. Then we remembered seeing a sign for gas, sold at a timber yard, so rang them and asked if they stock, and their price - £44, none in stock, but they can have one by Friday, so that's on order. This is the very same actual LPG gas, sold by petrol filling stations for vehicles, costs just £25 for the very same amount of gas. Someone is making an awful lot of profit, from selling bottled gas.