Not enough, apparently. She still got robbed of her iPhone and had to buy another one.
There was an interesting approach with VanMoof bikes where the company insured it against theft, and if your £2000 bike disappeared they actually had a team that would go to it's location and ask for it back. The police don't seem that interested in getting stolen stuff though - that was private enterprise.
Still I'd pay for that on a phone if only to get the bastards who snatch the things.