I went on a week long Northern European cruise, and to London for a week with my Mom last August. Had an AMAZING time. Flew from Seattle to Heathrow for $550 on a Virgin Atlantic deal. By the time the hotels, cruise, and airfare were paid, I paid less for myself to go and do all over 2 weeks than for just my daughter and I to go and spend 5 nights at the Poly with dining and airfare.
People think Europe isn't within reach, and I think Disney would like us to think that. It isn't, not even a little bit. If you plan 12-18 months out, or take a last minute deal, it can be much cheaper than WDW.