I am insuring a $5000 bicycle against theft in San Francisco, and it costs 0.5% the cost of the bike every month. I have no idea where you are getting these insane numbers from

I can insure my €4k electric cargobike for €7/month. I do have to use a €80 lock, but I‘d do that anyway.

Where are you getting your numbers from? I got my new e-bike insured for 2 years for 10% of the purchase price

Yes, if your bicycle costs $100. But why insure it then?

I just insured my son's new bike ($1500) for only $20/year as a rider on my renter's insurance

Less than 10% per year.