Even without a pre-cut rack, its pretty common that whatever you've locked up to (sign post, bike rack, parking meter, handrail, etc) is a lower grade of steel than the ultra-hard stuff on the shackle of a good bike lock or chain anyways. No need to pre-cut that cheap galvanized steel sign post if you don't want to, a thief would have no problem getting through it quickly if something attractive was locked up.
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)
