I bought a 80$ used bike at my local community bike repair shop earlier this year and I'm keeping it outside every day without getting it stolen.

I just bought a Kryptonite + a Kryptoflex and nobody tried to steal it yet. My locks were more expensive than my bike but it seems to work for now.

As a former kryptonite lock and bike owner, it works until it doesn't.

I use steel chain with steel lock[0] for last 5 years. No problems so far.

[0]: https://ae01.alicdn.com/kf/HTB1UMz3k8yWBuNkSmFPq6xguVXar/1pc...

I think the goal of that strategy is to reduce the cost of replacement as much as it is to deter theft.