Quirky pricing policy by Sensodyne or is it too clever?

Pricing is always a tricky part of the marketing mix. when you combine it with promo schemes, it becomes even more potent.
Recently in a supermarket I was shopping for toothpaste and came across Sensodyne's two SKUs. One, a 40 g,m pack for Rs 55. Another, a 70 gm pack for Rs 150. The size of the pack was huge and there was a promo of a toothbrush worth Rs 50 free. If you had not looked at the actual content of toothpaste, one would have been tempted to pick the larger pack. 

I fail to understand GSK's pricing and promo policies. Do you?