ScottyDogg It depends! From the little I do know, companies with their own import 'division' E.g. Bothners, Mars, Marshall will all get better pricing on the item they import than competing local retailers - compare Raru's pricing on Fender/Cort vs Bothners and you'll see what I mean
On strings 'n consumable's - it can be 100%+...(E.g. At Bothners, a set of Ernie Ball's retail at R120, should cost them under R60 landed). That's why stores love selling ya gig bags, capo's, cables, straps, etc - great $ spinner.
On guitars/amps/fx/etc...I'm really not sure. I reckon it varies quite a bit from brand to brand. How I think about it - check the big US retailers, figure out the lowest online price and then guesstimate that -at worst- that would be the landed cost in SA (ex vat). I reckon the local big importers (Musical Distributors, Rockit) bring enough things in to -at least- be able to land items at Sweetwater pricing. Not sure that's a fair way of approaching it though.