Yep, mine cost me $3 for the cap (which included a rear lens cap as well as the body cap -- I could combine the two and have a very, very small single-shot pinhole camera!) and took much less than an hour to make, including figuring out the best way to drill and countersink the cap; I could do another in ten minutes plus the time to make the actual pinhole.

Mind you, it'd be a lot easier to sell dozens in a day at half that price...