It works out at about £50 for the tour (take the exchange rate). There's a ryanair flight at 9.99 euro over, and sure, if you changed carrier there you could probably get a flight home for 20 or so. Would mean flying from Dublin though. I looked last night and easy jet seemed to have some cheap flights from BFS.
From what I can gather the interior of the aircraft isn't open to public, only to groups like this, but I may be wrong