Yes, I am too, I just went deeper than most... I work with locks for a living and a hobby. 20 years as a Locksmith now.
The two areas I collect are Unit locks made since 1899 and Cutaway cylinders. Mostly high security cutaways but just about anything that is cutaway in a lock cylinder.
This isn't entirely true. If you happen to come across a really rare padlock that can set you back maybe $1000 or more if it was for sale. But this all depends on what you consider to be expensive. But you are correct in that it is a place to start. Collecting is all about what you find that makes you sit up and your eyes light up.
No need to. Google Patents has already done it for us. :8): It is MUCH easier to find something with Google Patents if you put the right words and or name.