HZ is on the money here.

If you do the sums above you will invariably come out with around the same figure - give or take a few thousand.

The car in Perth for $17k may be too expensive - the market will decide. If it is still there in two months then it may be a bit too expensive. If it sells in a week then maybe a bit too cheap.

Like any collectable vehicle - they are worth what someone is prepared to pay.

Sandmans (whether original XX7 etc ) or not ie good reproductions, do not come up for sale that often and are maybe getting a bit harder to find. Thus the price will reflect this.

If you think about it all Sandmans are too expensive - they only cost $4k when new. See if you current Commodore is worth 4 times its new car price in 30years.