South Korea has a population of 50 million and subsidies there were tightened according to that report.
It also could have been a strategy between Samsung and the South Korean carriers. Advertise a ridiculously high price first then decrease the price will draw a lot more customers than advertising a suitable price first. It's a strategy used in marketing and it ALWAYS works.
South Koreans also pay more than Americans for the Galaxy S6 and we know that South Koreans also have lower purchasing power than Americans. So it was to be expected IMO. The same cant be said for the iPhone 6, where carriers subsidized it heavily last year in South Korea (and Japan) because of a deal with Apple.
The same doesn't apply to the US.
Furthermore, I would take that report with a grain of salt, considering it's only the first few weeks of release.
iPhone sales, however, seem like they've slowed A LOT.
Samsung widens lead over Apple in smartphone market
That was before Samsung released the Galaxy S6/S6 Edge.
Apple's market share could collapse to below 10% soon before Q4 when it releases its new iPhones.
Apple is most likely depending heavily on the iPhone 6S/6S+.
If they don't do well, expect Samsung's smartphone market share to reach the high 30% to low 40% range in 2016.