Self interest is only equal to cheap and crappy for people with no money, who incidentaly are also not a good source for economic advice.
Michael, I have no good idea what you actually mean by this comment? It seems to imply that poor people are idiots who will always buy rubbish unless the option is taken away from them, and need to be protected from having choice in what they buy, but I doubt that's what it was intended to mean?
Anyhow, self interest in this context means buying whatever provides the best value-for-money from a consumers experience. It doesn't mean necessarily buying either the cheapest option, or only crappy products. Depending on what someone wants and can afford, it can also mean buying the upmarket option (Mercedes instead of Lada), or paying a premium to buy local because of convenience, support and knowledge that the retailer brings to the equation. It can also mean importing something yourself if the local supplier is charging way over the odds compared to where it can be otherwise sourced, and not providing value commensurate with the premium they are seeking to charge. Retailer in this space will likely go out of business, just like other business models that have been overtaken by history. Ultimately, as detailed by Joseph Schumpeter, this process is beneficial overall.
You also seem to imply that NZ Consumers have some sort of moral obligation to pay over the odds to a retailer here rather than a cheaper retailer (in effect making a substantial charitable donation to that business), just because their owner is "local" and they employ people. They don't. And that sort of thinking ultimately takes you into the zone of protectionism, tariffs, quotas and import licencing - which can be made to appear a sensible economic strategy in glib soundbites, but doesn't withstand serious analysis, or work when tried.