Getting in the Pilbara requires flying to Port Hedland, Newman or Karratha via Perth daily flights by Qantas, or drive the very long route from either Perth or Darwin Port Hedland to Perth is 1650 km via the Great Northern Highway, 1770 via the Coastal Highway, and Port Hedland to Darwin is 2400 km....
Flights from Perth are expensive, but the cost varies greatly depending on the type of ticket purchased. The less flexible "Red E-Deals" are the lowest cost, but sell out quickly. Book well ahead to ensure you get a seat at a reasonable price.