Andrea,
Yep you are correct - Ryanair are paying for the taxes in this promotion. There's no such thing as a free lunch, the cost has to be taken by someone! I could be wrong of course and Ryanair might not be paying directly and/or are using some kickback deal or using some funds they were due or something like that, but from the 'Provider' and 'Customer' perspective, then Ryanair are taking the cost of the tax to help do exactly what haunted mansion did - tell alot of other people which increases the chances of more people booking and thus making Ryanair more sales!
Even though I know I can't go away at all right now, it still made me log onto their page to see those fares!
Haunted Mansion - enjoy yer almost freeby flights and time away! and cheers for letting us know, one day I might be able to get a couple days off in the med or something!
Cheers! DtM! West London & Slough UK!