We have a family holiday booked for Easter 2016, and had the same problem. We wanted to collect in Alice Springs and return in Uluru - which meant the companies we could deal with were restricted. We did not find any that had unlimited kms, or allowed any unsealed road use (which meant we had to upgrade to a significantly more expensive large 4WD to take it to the areas we wanted to explore). Hubby rang the company directly, and we managed to get $1000 off the best internet price. Talking to the person in Alice Springs also helped us - told to collect from the township not the airport saves a lot (even considering the taxi fare). We also got a discount belonging to the RACT. Also watch for conditions about driving the car after dark.