Surfer here, spent 7 years in remote coastal south america surfing fairly regularly.
It's not that they're made overseas -- it's that the basic method of manufacture he mentioned, "pop-out", in the industry implies using a plastic shell and then pumping foam into it, and a few other similar methods of manufacture.
For shortboards, it's pretty terrible. The boards are very heavy for a surfboard, with poor rigidity and flex, and in fact they don't even attempt to target the "real shortboard" market, where extreme light weight, stiffness and a very delicately balanced flex work together to form something that lets you nimbly glide along a decent-sized wave on a board slightly shorter than you are.
Basically, the best form of manufacture for surfboards is a core of either high-quality rigid foam (not the heavy, flexible foam used in wavestorm/some pop-outs) or air, covered in substances like fiberglass and/or carbon-fiber fabric and minimal amounts of epoxies (sometimes using the same vacuum techniques as other carbon-fiber manufacturing to minimize weight). I said 'foam or air' because for a while people have been predicting that we'd move to hollow carbon-fiber boards, and there are/have been some of those boards, but they have their drawbacks and are often expensive.
Can performance surfboards be disrupted? It's already happened, to a certain extent. Channel Islands and other surfboard brands use automated milling of the foam blanks, and other automated processes as well.
Too, any overseas contenders have to worry about shipping. Surfboards are huge -- you could fit 20 boxed iphones in the footprint of a single boxed shortboard. At the price points mentioned ($300-$500), overseas shipping would probably eat into your margin. Shipping is even an issue for domestic producers; often shipping a board halfway across the country can cost $50-$100. Which is a nice bit of extra margin for a local shaper and his customers.
When will good surfboards get cheap? Probably when great carbon-fiber bikes get cheap, ie, when carbon-fiber manufacture is so well mastered by man that designs in any shape can be pumped out like Lego.