...... According to the seller it was the last one sold in australia......
Well I know that's not true. I bought my ST13 new in August 2013.
What's it worth is the question! If he's asking $18K, it's probably more than he paid, if he got the discount. In April 2013, he should have.
If, if, if ......... if in 2015 Honda were still selling the ST13, if the RRP was $24,990 (I think that was the last RRP), if top box $1K (same $ as mine), on-road costs around $1K, this would place a new ST13 at around $27K.t I'm not sure everyone would be too worried about paying $18K for this unit with 3,000km - IMHO.