These tricks in advertisement claims are nothing new....hell...I learned about this in elementary school. It's normal to hype your business the same as the average person hypes themselves up to others to make them "appear" better than they are. The consumer is responsible for educating themselves when it comes to fine print...(did I mention this is taught in elementary school?)
I find people who get suckered into these claims are more victims of their own compulsive shopping habits than the big evil businesses taking advantage of them.

Besides even if Walmart saved 2 families an average of $2800 a year then they are being truthful...they don't say every family...just families.