The first two were bought used as I had kids too. It wasn't until 1985 that I pushed the boat out and bought a new OM4 - I'm pretty certain it was a little over £600 which was a big lump of money for me at the time.I remember lusting after the Olympus OM1 when it came out but finances dictated sticking with my Chinon.
I think this was what I had in mind, a camera good enough to do 'photography' with. My family had an old box brownie that was used to record family events etc but clearly didn't cut it for 'taking photos seriously'As others have said, "What is a serious Camera?". Probably any camera, that we use to take photos seriously with.