IIRC, the scanner law only applies to 10% of the difference up to $5.
Retailers should not be held accountable for accidentally displaying wrong prices. Nobody is perfect. If it's a bait and switch however, there ought to be penalties.
As a web programmer, I can certainly understand how a mistake like this could occur. What Amazon could do is offer a $25 or $50 gift certificate for those people affected, just as good business policy.