The more I read on this thread, the more I regret booking my September flight from IAD to LHR via DUB on Aer Lingus. I do have the option to change but the fares for next year are so sky high at the moment, it might be cheaper to (1) cancel and recover the taxes and (2) re-book (on another airline) next year when the fares have (hopefully) declined.

With that thought in mind, I had emailed Are Lingus 10 days ago:

Me: I have reservations which include $600 of taxes. How much will I get back after fees, penalties, etc if I cancel?
Aer Lingus: You have $600 of taxes on your flights

On the bright side, I do appear to be a candidate for "The Dublin Dodge" .