As far as singles go, MAF had a C207 with around 20,000hrs and a couple of C207 in WA with 19,500hrs.
With the average age for a GA aircraft around 32 years, most have been owned by a few people/operators. Aircraft like 210 and 310 have probably been used as a private aircraft at one stage, as this was there original market.
Aircraft like a C207 or a Cheiftain/heavy twin were marketed for commercial ops and hence will generally have many more hours as they probably haven't been sitting in a hangar and only taken out on long weekends.