Amazon UK offers Battlestar Galactica: The Complete Original Series on Blu-ray for $25.71 (£20). At checkout it drops to $21.43 (£16.67). With $3.96 (£3.08) for shipping, that's the lowest price we could find by $20. The nine-disc set includes all 75 episodes.
Note: Although the episodes themselves will play on U.S. Blu-ray players, the extras and special features may not. Allow up to two months for delivery.