Probably close what you paid for it at auction? Since that is what the market has dictated is the value?
I believe it went to $17,500 and buyers premium is 7.5% (including GST). So what's that $18,812.5? + Freight to Queensland? Maybe $1,000 on top? So around about $20k?
But I hear you're asking closer to $30k? Sounds like your circumstances change often.
And full disclaimer, I have no problem with people trying to flip cars.
What I do have a problem with is people doing so under false pretences and using a community forum like this which costs money to run each month as their platform for doing it. As no doubt you'll be in and out like a flash in the pan, having just enriched your own pocket.
Just be transparent that you're flipping it.