This discussion on the 4x4 forum hits the nail on the head:
One of the questions I have pondered but never fully understood is the churn of 2nd hand equipment being advertised.
The honourable Fluffy posted this response which explains a lot IMHO:
It is not an easy game to be in, which is why I haven’t ventured into it full time.
My son-in-law has an established electrical contracting business, and a large part of his operation is PV Solar system.
When load shedding happens, everybody want a system yesterday. Suppliers don’t have stock and their prices go through the roof.
So you buy all the stock you can get and “poof”, load shedding stops, and you cant give the stuff away.
People fiddle and do crazy things, damage the equipment, and you carry the can. Even if the equipment is still under manufacturers guarantee, you must diagnose the fault, send the system away, laise with the supplier, get it back, install it, and often have to lend them an inverter while all this is going on.
If you sell them a system that is too small because that is all they are prepared to spend, six months later you sit with battery replacement and no guarantee.
If you try to sell them the “right” size system, it is too expensive and they go next door for a “cheap” system.
And the list goes on …