Hi,
Not sure ... but I would talk to an Accountant real quick. It depends a lot on how you market yourself and how your group is represented. If you are free-wheeling, I would recommend having the equipment insured, but if it is so cheap that it is not worth the cost, then ... fine ... go to the store and get another crapper to fiddle on!
If you are registered as a business entity, and you probably SHOULD, then your equipment is an "asset" and can be depreciated and worked over and it will help your tax base. And if so, the insurance costs are also deductible!
It all depends on how smart you are, or want to be. If you have a guitar that cost 5K, yeah, I would ensure it. If it cost $100 bux and it is worth just $50, I probably would let go, and then pull a Jimi on stage once in a while with it, if you feel the need!
This is something that you want to spend a couple of bux studying first ... and I would talk to a music business accountant (not book-keeper), or a music business lawyer if you can affort the 200 or so for an hour to yap about this stuff so he can advise you.
A bit of legal advise, goes a long way ... it all depends on your level of acceptance and desire to handle it ... but putting away 3 or 4 dollars per week is not important to you ... what's the point of asking?