[short_circut]

I wonder how much patent licencing adds to the cost. The author mentioned how wonderful of an idea this bimetallic strip was, but that means someone invented it and someone probably holds a patent on it. How much does it cost to use that innovation?

[uiri]

Should be $0 since http://www.google.com/patents/US2987607 ought to be expired by now.

[code_duck]

It's probable that that invention is old enough that is not currently under patent protection.