Renters insurance is cheap and totally worth it, not just for your bikes but for everything you own.

You can also get policies covering specific things you own that need 'extra' insurance. For example my parents have a small art collection in their house but their homeowners insurance only allows a certain percentage of the policy to cover art so they pay an extra $40 a year to cover the paintings. My wife has an additional insurance policy on her engagement and wedding ring as they are worth quite a bit. If you own several fancy bikes that need protected, you should talk to an insurance agent about what coverage is available. If you don't want to pay the $200-$300ish a year for renters insurance you might be able to get a policy that just covers your bike(s) for less money.