The majority of tourists to Bali are from Australia. Bali is the closest to home they can go without going to NZ (similar to Australia) or staying in country (ignore Papua New Guinea as too dangerous).

Planes make Australia a lot more viable, since it’s such a huge sparsely populated island that even a lot of domestic travel is better in the air. Bali and Indonesia’s various small distributed islands are much more dense, but island hopping by boat alone is also slow and unsuited to a lot of economic development.

Countries like Australia and Indonesia would take huge hits if air travel was a lot more expensive, much more so than America.