soundbase You say new guitars aren't subject to customs duty, do you know how much you are subject to customs with a used guitar.
AFAIK it's the same - Secondhand imports (IIRC) used to be a loophole to avoid vat, but that was a loooonng time ago.
Just looked up the calculation of vat for importing on the SARS website (you're welcome)
To calculate VAT on imported goods, the ATV (added tax value) needs to be determined first.
This is done as follows:
[(Customs Value + 10% thereof) + (any non-rebated duties levied on > the goods)] x 15%
= [ATV] x 15%
= VAT payable
The 10% mark-up on the customs value in this calculation is applicable when goods are imported from a country outside the Customs Union. Therefore, if goods have their origin in any of the BLNS countries (Botswana, Lesotho, Namibia or Swaziland), the 10% will not be added to the calculation.
When goods are exported to any of the BLNS countries, the same applies (no mark-up on the customs value to determine ATV).
soundbase And also what are the issues with bringing in a. guitar with rosewood?
Anecdotally, I've heard a personal import should be fine...though the rules could be applied arbitrarily. Here's a couple threads from last year: 
#264935 and #27051
