If you are not going on your own, then I wouldn't do the tour. If you are alone, the tour makes a lot of sense.
Try skyscanner.com.au for up to date prices, I used it yesterday to price up Melbourne to Amsterdam and it appeared to show me all the competitive fares.
I did Oshkosh a few years back with Beechie and Jabba and a few others. They found their own way there via Green Bay, I went with father-in-law via Milwaukee.
I posted my itinerary and costs on here a few months back - it went something like this:
- Mel - LAX
- 2 nights at LAX Hilton, visited Univeral and did an LA tour
- Airtran to Milwaukee
- Amtrak bus to Oshkosh
- We stayed at Fon du Luc Executive Lodge (not cheap), but Uni would be fine (you'd need a car otherwise)
- 5 days at OshKosh which should be enough (slightly cheaper if you join up)
- Bus back to Milwaukee (Harley museum visit)
- Flew out to Tuczon Arizona
- Stayed at LaQuinta near airport 3 nights
- Visited Pima air and space muesum + Arizona military boneyard
- Visited the Titan missile museum
- Didn't go near Mexico as they were kidnapping and behedding at the time (It's just down the road a bit)
- Hired a car and drove via Phoenix to the Grand Canyon (4 hours drive), through Flagstaff, quite scenic
- Stayed right next to the Canyon at Xanterra logdes 1 night, very scenic in the woods
- Had a good look around the GC park, museums etc, can catch a heli down the bottom if you want, Maverick choppers had a dozen EC120's there
- Drove to Vegas, about 4 hours.
- Stayed a couple of nights there, did the usual walking around and it was HOT. So HOT at midnight it was like a hairdryer in your face walking around outside.
- Drove back to Vegas (4 hours) and visited Manhattan and Venice beaches etc.
Driving isn't that hard, just put a Nav program on your phone and follow your nose. Alternatively we would have flown home out of Vegas.
This cost all up $3,100 each excluding meals. Flew over on an A330 via Auckland and back on the A380 to Melbourne, including OshKosh tickets, Universal Studios, hire cars and all accommodation (more expensive than the Uni).
I understand that a simple tour exclusively to Oshkosh for a week could cost you roughly the same as this. Our trip was just over 2 weeks.