Amazon.co.uk offers the Robin Hood and Gladiator Combo on Blu-ray Disc for $12.11 (£7.50). During checkout, it falls to $10.09 (£6.25). With $4.97 (£3.08) for shipping, that's $18 under the lowest total price we could find for the pair when purchased separately elsewhere. This 3-disc set features Robin Hood (2010), Gladiator (2000), and deleted scenes.
Of note, although the movie will play on US Blu-ray players, the extras and special features may not.
Robin Hood 2010, a similar product, is available at these stores