We got a wicked van, bout $65 a day then you can camp out right next to the beaches, in fact over 2 weeks we only paid to stay 2 nights at coral bay for the showers, and to refill water, etc. Rest of the coast you can find somewhere free to park the van up. At Exmouth start the day with sunrise snorkelling at oyster stacks (mind blowing) then kite the arvo.
Plus we got one day free van hire for turning up to pick it up naked. Lots of surprised backpacker girls in the office