Telkom's per Gig pricing for ADSL has nothing to do with WBS/iBurst. They buy their bandwidth from UUNet & IS. These two in turn buy raw circuits (on SAT3) from Telkom to connect their S.A. networks to their POPs in London & NY.
Totally different product/department at Telkom, so no I would say it will have no direct impact on WBS's bw pricing ... but of course there is always natural market pressure.