Reasonable? Hmmm....Well, I suppose with business liability insurance it is a lot like the phrase "reasonable attorney's fees" when it is used in conjunction with the enforcement sections of contracts. It is a bit of an oxymoron. No offense to the lawyers out there, but, I digress...
At any rate, I too grapple with how to deal with the costs associated with liability insurance for my sound company. So long as everything goes smoothly and I never have to make a claim, carrying the insurance is a necessary business expense. Without it, many potential and existing clients will not consider hiring me. OTOH, just because I am insured does not get me the job. I have to maintain a relationship with a good insurance company, one that also has as good a reputation for solid financial management. I have a couple of clients that check the rating of my insurance company, and they will except nothing less than an "A" rated carrier.
For that reason, I spent a considerable amount of my time researching what agents and insurance companies write policies for sound companies. From what I learned, it is wise to consult an insurance professional with experience in the entertainment industry. It helps because when the agent goes to look for a company to write the policy and give a price quote, they are working with an insurer who has written this type of business insurance before, and understands the market.
You can find yourself spending many hours answering seemingly bizarrre questions from insurance underwriters if you deal with people without experience in our field.
If you can avoid the above mentioned pitfalls, and find a good insurer that you can afford, the cost of keepig your insurance should become a part of your business planning. I allow for a percentage increase in the cost of insurance each year, because even when not making claims, it seems like the costs continue to rise. So long as the insurance price hikes don't become absolutely outrageous, I can plan for my insurance costs in my financial and business strategies for coming years.
Bottom line is to shop around and do your homework. Part of being in business is dealing with this stuff. Not as fun for me as doing sound at the gig, but every bit as important. Sorry for the long answer.
-Marc