Shop around. It helps if you're a member of a professional association that offers some sort of a special package through an insurance company.

We found a company that insures all of our bikes with no limit. Only the regular deductible would apply. This was a group offer for my husband's medical association. With our initial insurance company it would have cost hundred of dollars per "nice bike." Our commuter bikes would not be covered due to the deductible, but for the fast bikes it's peace of mind.