Mathematics or basis for survival?

I found unique price tags in a glossary store. There are two sizes and three variations of the price toward an item.

1. 140g 500 yen
2. 200g 1000 yen

3. The price tag says if I buy 2 packs of 200g, I can get 2 for 1500 yen.

Which do you think is the most valuable? Sometimes we are tempted by the message in the tag. However, in this case, first one(140g) is the most reasonable. If you buy 3 pieces of 140g pack, you can get 420g in total by 1500yen. If you believe the card, you will get 400g by same price.

cafetalk math, 14-05-26 22:38, 14-06-30 17:15, Yosei