I am getting the feeling that the reason it was so cheap is that board looks like garbage. A sort of just get these ones out of here type price.
Possibly, but Hobby King have been selling these at this price for quite a long time, and I'm fairly sure they sell out and restock on occasion, so it's obviously something they still get their hands on. I can't imagine there is much money in it, but realistically there's not many components involved either, the biggest cost must be the transformer.
The transformer is also the biggest cost in buying this thing due to the shipping, I think to ship that to NZ it would make that $16 USD soldering iron into a $60 USD soldering iron.
Which is much less of a deal.
I don't know why switch mode supply DC driven irons are not "a thing", I have one (chinese driver, running off a laptop supply, using the typical 900 type handle), it does the job just fine, for a hobbiest, way smaller and lighter, in one my bodged together coreflute enclosures.