I'll use about $100 worth of u-locks to lock up my not-super-visually-impressive $250 spare parts city errand bike as long as overnight (and this is in NYC).
But I think the strike point where spending more on heavier/fancier locks to secure a more valuable bike just stops making sense is right about at the price point I'm already at, most nicer bikes are simply too nice to leave unattended on city streets in the US or anywhere else where bike theft is a concern. Someone with a good set of pocket tools could rip $500 worth of parts off a well-locked frameset and wheels in 20 mins without making any noise... and I don't think a non-cuttable material helps that scenario, even if it does make very secure locks attainability light.
(Could be a really big deal for bike touring folks though, who often ride out with a cheap cable lock at best because anything better is too heavy to carry for days/weeks)
Way back in highschool this always used to baffle me. You'd get kids spending $50+ on super fancy locks for their lockers, but all these locks equally were fastened to the locker with a flimsy little hasp that you could cut with a pair of tin snips, assuming you didn't just bend back the door of the locker itself.
If you have a nice road bike with very clean tires people generally will not mind you bringing it into places with you consistently.
No matter how good your lock is, if somebody REALLY wants the bike (for the value of its components) they'll just saw the frame in half.
I've also had 3 bikes stolen, the rear wheel stolen, the basket stolen, the front brake stolen, the seat stolen, but now with all the locks there is much less stealing.
It's a target, but it's certainly not a "juicy" target like, say, a $3k mountain bike.
The bike thieves continue to steal the small stuff, notably the rubber attachments which hold my bike lights, but haven't been able to steal the big stuff (frame, wheels, basket, seat) in a long time.
One of the strangest things that was stolen is the yellow electrician's tape I used to "dog" my seat with—they painstakingly peeled off the tape, but left the seat.
What is the cost of it? A few bucks? I can’t even be bothered to sell my used crap on eBay.
Edit: I am wrong!
This is because unlike a gun, there is no need for the gases to release to the outside openly. Therefore, there is much, much less noise, and it doesn't sound like a gun at all.