SKG-ATH is normally incredibly cheap - maybe as low as 19 Euros if you get a sale for the right period. Ex-ATH is always more because of the taxes, but SKG has the advantage that FR also fly the route (I think, still), so if you only need a single flight you might be able to mix and match to get the cheapest overall deal.
Distance is not usually the driver on price - competition, subsidies and load factor are.