Butane is more commonly used than propane.
Gas is expensive because this is a small country and the gasoline is imported. Gas is expensive in many countries, when compared to the price in the USA.
A few years ago crude oil was discovered in Belize. But the source has almost run dry now, unfortunately. Also, there is no refinery in this small country. So even the crude oil Belize did extract had to be sent out of country to be refined. So the transport adds quite a bit to the cost.
This is a very small country, with only 330,000 people. We don’t have much industry here. Tourism and agriculture are the primary money drivers for the economy of Belize.