An interesting little experiment is to click on the different flags on the Ryanair website and note whether the "headline" fare is inclusive or exclusive of taxes and charges. The general rule seems to be "exclusive, except when national consumer legislation insists on inclusive pricing".
So for example the French, Dutch and Danish flags all lead to inclusive headline prices.
Katana.flyer: there's nothing to stop an airline breaking out the charges that make up a total. However the issues are twofold:
1. showing an attractive headline price to sucker you in, and then adding a relatively large sum late in the booking process could be seen as misleading, no?
2. the "taxes and charges" are by no means all government-related. Indeed, not all the airport charges are even real charges. It is quite common practice for an airline to show (for example) 10 pounds airport charge per passenger, corresponding to the published standard airport tariff, and to charge each passenger this, even though the airline has a private commercial deal with the airport under which it pays (for example) only 5 pounds per passenger. Extra profit on the bottom line for the airline, along with the ability to "blame the airport" for the extra costs. (And don't even get me started on the profit margins for the airline inherent in "wheelchair charges" and "credit card fees".) So I think it's rather naive to suggest that exclusive-of-tax-and-charges fares are in some way fair and transparent.
A topical example of this is in the current Wizz Air vs SkyEurope handbags-at-dawn battle of press releases (about which I posted on
this thread. SkyEurope in passing accuses Wizz Air of inflating the "taxes and charges" element of fares:
However, SkyEurope will always remain fair airline and brave to cut underperforming routes as the only listed and transparent low fare airline in Central Europe, which can be demonstrated also by not charging its passengers hidden surcharges:
Wizz Air's taxes & charges SkyEurope taxes & charges
Warsaw up to 102 PLN Warsaw 30 PLN
Katowice up to 116 PLN Krakow 48,90 PLN
Budapest up to up to 7410 HUF Budapest 3125 HUF
Best regards
C.