Amazon UK offers The Coen Brothers Collection on Blu-ray Disc for $14.70 (£12). Add it to your cart and it drops to $12.25 (£10) at final checkout. With $3.77 (£3.08) for shipping, that's the lowest total price we could find by $10. It includes A Serious Man, The Big Lebowski, Barton Fink, Burn After Reading, and Intolerable Cruelty.
Note: Although the movies themselves will play on US Blu-ray players, the extras and special features may not.