Suggestion: The Special Eyes at 1.33–1.66 ref

Conclusion: Before you say something stupid like "Not enough proof, downvote", take a look on the market first. This thing is so rare now. Demand > Supply because supply of craft hats went down and it's reasonable for this thing to rise.

Feel free to counter / support my proofs.

The lenses can be painted and they change to match the Engineer's expression. They also glow in the dark.

http://www.youtube.com/watch?v=NOWibpRHHBI

That's actually creepy.

Is there a reason these are still rising?

Yes

Supply decreased, demand stays still as people still want hats to wear => Rise.

Makes sense. ~~Blind~~ upvote as usual.