Amazon UK offers the Harry Potter: The Complete 8-Film Collection on Blu-ray Disc for $34.68 (£27.99). At checkout, the price drops to $28.91 (£23.33). With $3.82 (£3.08) for shipping, that's the lowest total price we could find by $6, although we saw it for $7 less Black Friday. (For further comparison, it's $17 under our mention from a week ago of a digital copy.)
This Blu-ray set is region-free, and the films themselves will play on US Blu-ray players, but note that the extras and special features may not.