I've had some nice success at Bargain Hunt over the years. Nothing like that as far as savings, but here are my best finds:
Arkham Asylum 10937 for $100
Tower Bridge 10214 for $120
Both of these sets had been opened, and the desk staff were kind enough to let me check the contents before purchase. Arkham was easy, the bags were numbered, but Tower Bridge isn't numbered and has over 30 bags. I think they're all there, but worst case it's an awesome deal on parts. Arkham was only missing one common piece.