Another thing to throw into the mix, there is the possibility of of an AD for inspection/repair of wing spar caps in PA28 series aircraft being made in the US.
https://www.federalregister.gov/docu...-inc-airplanes
If that happens expect it to be applied here.
I am aware of several PA28s in Oz that recently have been inspected pre-emptively and have shown evidence of damage and so would be wary of buying a PA28 without having that inspection done and the spar repaired/replaced if it shows sign of damage/corrosion. Best to talk to a LAME about this first - I am not a LAME so going on what I have seen/read around the traps.
Rectification will be an added cost and time consuming if damage found and may make a bargain purchase a liability.
Nothing against the aircraft but most of them are getting old and may have a history of work that has placed stress on that area (particularly ex flying school aircraft).