The competitive environment of the budget airline is one in which they all try and maintain a competitive edge. Virtually all use advertising to lure us into buying cheap flights, and more often then not the price they quote does not include taxes, unavoidable charges, surcharges and fees.
This is how you get the infamous 99p flights.

The BBC reports on how the European Union want to stop this “false” advertising.
“You or I might see an advert for an airfare for 99p,” British MEP Robert Evans says. “But we’ll end up paying £99. Those ads are misleading – and it’s great this regulation will stop them.”
The new law agreed by members of the European Parliament means that all taxes, unavoidable charges, surcharges and fees will have to included in the advertised fares airlines offer.
The report is interesting and useful as it explains how the changing business environment is forcing budget airlines to change the way in which they market their cheap flights.