If you are going as far as
Alice Springs then it is worth the extra $300 for the trip to
Uluru-Kata Tjuta, but if you had no plans to go through the outback, then it is a big detour to take to see the rock.
Personally I think a road trip through the outback is an essential Australian experience. Although nice, so many Australian seaside towns are unremarkable and they can feel the same after a while; however the outback is a unique experience. It may be a long boring drive (or train trip) and it is a place you wouldn't dream of living, but it is a one of a kind experience. If you are making the trip between Adelaide and Darwin and stopping at Alice Springs on the way, then take the three days (and $300) out of your schedule to visit Ayers Rock.
Uluru isn't the best thing is Australia but you'll kick yourself if you have the opportunity to visit but don't. Also I think that
Kata Tjuta is a more interesting destination than Uluru (although virtually all the tours from Alice Springs take you to both).
Consider that for a 3 day/2night trip that is around $100 per day and you would pay $50 a day if you were just to sit in a hostel by the beach and do nothing. In that case the extra $50 a day is worth it.
There is also the option of renting a car for a few days and spliting the cost with other travellers. In some cases this can work out cheaper and will give you more flexibility; however most rental cars can't be taken on unsealed roads which rules out a detour via the Merrinnee Loop Road (linking Kings Canyon and Glen Helen Gorge), which are included on some of the (more expensive) tours.
Ayers Rock
Linear Mode
