This is so cool! We were just discussing with my family the other day about how Mr. DIY stores have this effect you mentioned. Mr. DIY has cheap items that you don't even need but because it's cheap, you pick that item up and without realizing it, you're at the cash register with a basket full of these items and poof - there goes your 2000 pesos.
Grocery store people are clever. We need to be more clever than them!