My cousin tried the really cheap bike route. I think a little over $100. Lamentably it didn't matter, it was still 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.
[0]: https://ae01.alicdn.com/kf/HTB1UMz3k8yWBuNkSmFPq6xguVXar/1pc...