First, there isn’t any lock in existence that cannot be cracked. From bolt cutters to hydraulic cutters, normal lock-picking tools to electric vibrator pick tools—it's all a question of noise level and time and common sense regarding parking location. (I once took a picture in front of a 24-hour police station where only a bike frame dangled on a bike stand.) Even cutting the frame with a £5 hacksaw to steal the electric bike parts, including the RockShox fork—forget about the frame as an option! Or just grabbing a Bosch battery worth £600 is not unheard of.
Here in Leicester, we have a £1-a-day bike parking facility with lockers and showers for commuters, which is brilliant (as well overnight or even a few days!) - for short stops to buy something. I park my bike where I can see it. There was a gang that stole racing bikes in Richmond Park by using an electric bike and robbing lonely Lycra-clad cyclists by threatening them with a knife—just like Rolex watch wearers have to endure while walking the streets of London.
Whether a lock costs £20 or £200 is secondary because if a bike is targeted, it’s gone. I just hope I never become a target or can’t keep an eye on my locked bike. Otherwise, I’ll leave my bike at home and take a taxi. It’s sad, but that’s the only way! (For me)