If you're spending 500 hours a year in the helicopter and your pax spend 1/2 hour a year, then an honest risk analysis doesn't justify the pax spending $500+ on safety gear.
For you, however, it may be worth it. Don't wear synthetics next to the skin (including Nomex), do be comfortable and functional. I always plan to wear full length cotton underneath Nomex. Sometimes it's hot. If comfort becomes a factor I may change.
As far as your passengers, don't wear a flying suit that is oil stained, sagging, torn, etc. You can look as professional in a flight suit as you can in a business suit.
If pax are still concerned with you having safety gear and them not then maybe its worth it to have some safety gear for them to use. Could even charge them for it.