From my understanding of this article, the Philippines have not...

From my understanding of this article, the Philippines have not been receiving the full price because they are unable to supply the ore grades they had promised.

Revised Gross Revenues for Shipment 13
Based on final assay results and price adjustments, the thirteenth shipment of saprolite ore previously completed by AMVI on April 27, 2015 (as reported in news on May 6, 2015 ) yielded a final gross revenue figure of US$1.73 million . This is due to the final assay results being 1.67% nickel grade instead of the previously reported 1.73% nickel grade, which translated into a reduction of gross income from the previously reported US$2.9 million to US$1.73 million . ​

That is the massive difference between higher and lower grades.
The full article:
http://www.*****.com/news/2015-07-1...ata-Nickel-Laterite-Project-In-June-2015.html