Package has a better price bar 10-pack of 2.1 ounce bars cost 15.3712- pack of 1.4 ounce bars cost 15.35

Hmm... well, the 10-pack of 2.1 ounce bars cost $15.37: 

So that means the price per bar is: 15.37/10 = $1.537
The price per ounce would be: 15.37/(10×2.1) = $0.73

For the 12-pack of 1.4 ounce bars that cost $15.35: 

The price per bar is: 15.35/12 = $1.28
The price per ounce is: 15.35/(12×1.4) = $0.91

In other words, the 12-pack has the better price per bar. 

Although, the 10-pack has the better price per ounce.