Amazon.co.uk offers the Harry Potter: Complete 8-Film Collection on Blu-ray Disc for $26.73 (£16.99). At checkout, the price drops to $22.27 (£14.16). With $4.85 (£3.08) for shipping, that's $13 below our mention from two days ago and the lowest total price we've seen. (It's a current low by $21.)
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.