While this is true, international demand may dip quite drastically due to the period of upheaval that would surely precede, and continue for some time after, any such Grexit. Demand dipped quite dramatically during previous iterations of the ongoing crisis, and any possible Grexit would almost certainly show even greater levels of upheaval - particularly if it came with a change of currencies.

This report is probably out of date - I doubt Aegean/Olympic still has a 90% share of the domestic market (see below), though the foreign operators now operating in the Greek domestic market could quickly exit the market should future dips in demand - like the 26% fall in domestic demand mentioned in that article - occur again, especially if accompanied by reversion to the drachma. Ryanair, in particular, would show no hesitation in exiting the domestic market if it no longer deemed services viable. However, international demand would likely pick up again quite rapidly after any post-Grexit stabilisation, on the assumption that a devalued Greek currency would make Greece an attractive destination, price-wise, for foreign tourists.

Those domestic charges are likely to be hiked upwards in such a scenario. And don't forget that the largest component - fuel - will still be priced in another currency even when used solely in the domestic market.