[yuliyp]

It's interesting you used Frontier as an example. Frontier's whole business model is "unbundle everything the law allows." This means dirt-cheap fares that alone can't cover their costs of running the flights. They need the fees to make the whole thing work.

[boring_twenties]

The last Frontier flight I took had the following cost breakdown:

Airfare: $0.01

Taxes and fees: $18.97

Total: $18.98