Geektastic:
Your first argument fails because you make the false connection between 'overseas investors' and the outcome, whereas in fact the outcome is not dependant on the bidder being overseas based - any bidder, even one from Bluff, son of 5th generation Kiwi, doing the same would have the same outcome.
But, we dont have buyers from Bluff bidding up the auction as they can afford it. But if you have one foreigner at each auction, thats what happens. A $500,000 property sold at $650,000 is wow, but to the foreign buyers, its nothing. For many its a good buy based on where they come from. And as they are moneyed up, its no matter.