I wonder if, when fire was relatively hard to start but highly valued and cherished once started, there might have been a sort of early economy formed in the trading of fire. Imagine a fire merchant, who has found a way to carry portable fire, perhaps a series of torches where a new torch is lit when an old one gets low, and goes to villages saying "I will use this to light a campfire for you in exchange for....."

The interesting thing about selling fire would be that it multiplies naturally and isn't a limited quantity (once you have one fire, you can use it to create fifty others fairly easily) and this means it would behave economically more like software or music and less like manufactured widgets. The infinite "copy ability" of it means that the more popular it becomes, the cheaper it gets, breaking the assumption behind supply and demand economics that popular things get more expensive. It would be like software, where if you want to buy something for which there's only a few hundred customers in the world, you pay thousands of dollars for it, but if you buy something for which there's millions of customers for it, you pay like $40.