The "paid for itself in one inspection" part is what gets me. I always figured those cheap Amazon scopes were junk and you needed to drop a few hundred for anything worth using. Then a buddy showed me a $40 one he'd been using for a year and it worked fine for peeking into spark plug holes. Changed my mind pretty quick. For basic stuff like checking carbon buildup or seeing if a valve is toast, you don't need the fancy tool. The math on saving one teardown makes it a no brainer.