$50k is hard to tell... slightly easier as a rule of thumb is to...

$50k is hard to tell... slightly easier as a rule of thumb is to take total luxury car tax receipts and divide by the threshold price for fuel-efficient vehicles (~$65k in 2017/18) and then divide by the tax rate (33%). (about $700m/(65k*0.33)) In 2017/18 it gets you to about 33k vehicles. This would be an upper bound as the average price is likely to be higher than the minimum for incurring the tax. Of course, some more expensive vehicles don't attract the LCT, if the buyer has an ABN (ie commercial vehicles) for example, so this will at least partly offset.

Calendar 2018 recorded ~1.15m new vehicle sales, according to vfacts data. It would be fair to assume that most vehicles sold are cheaper than $65k when new.