Hello John,
well, 2.800 USD is a lot of money. The OEM 986S axles should be able to handle around 500 Nm in normal street use. But on the drag track that might be different, because of a different grip situation - less slip.
Also maybe it's good that the axles are the weak part, because if you always would need a new gearbox or differential this might be much more expensive journey.
Regards, Markus