The idea that manufacturers would raise prices simply because a product lives longer flies in the face of Econ 100. Any time you raise prices you increase the opportunity for competition. Any improvement without raising prices gives you a competetive advantage.

It may be that the longer life comes at some cost to the manufacturer. That can safely be added to the price because any competitor would also incur similar costs to add similar value. However, if the additional cost adversely affects the price per unit of life it could very well hurt the manufacturer. A $10 wrench that lasts 10 years could be perceived as a better choice than a $15 wrench that lasts 12 years. And of course it would be a better purchase than a $12 wrench that lasts 15 years for somebody who loses their wrenches about every 8 years.

So single-factor Econ 100 homework might be over-simplified, but the principle should not be ignored.