This isn't an issue of boat cost or survey cost.
Insurance protects you against liability from damages attributable to you or your boat. It will protect you from environmental liability, personal injury to people either on your boat or another boat involved in an accident, it will indemnify the marina at which you store or dock the boat (often a prerequisite). I also provides financial assurance such that you can replace stolen or damaged equipment, personal effects, outboard, dinghy, etc... then there are worker's comp claims and medical payments for which you could be liable as well as uninsured boats. Most of these are not covered by simple liability insurance.
Both in terms of your own interests as well as protection of the rest of us, it is almost irresponsible to not have insurance which almost always requires a survey as a prerequisite, regardless of how much or how little capital you have invested. The good news is that, if the boat is not that expensive, neither will adequate insurance.