I think this calculation neglects the GET contributions from tourists who annually spend $7 billion on Oahu. 

Assuming a family of 5 spends $40,000 a year of GET-taxable goods, that would be $8,000 per person.  $8,000 per person x 1 million people = $8 billion. 

So, the amount of end-user sales is $7 billion (tourists) plus $8 billion (residents), which is $15 billion. (Note that Oahu GDP is about $40 billion, so this $15 billion end-user purchases is plausible.) 

If we assume that the $7 billion in tourist purchases goes through the same number of "baked ins" as the $8 billion in residents, then 7/15ths of the $200 million rail tax revenues is paid for by the tourists and 8/15ths are paid for by residents.

$200 million x 8/15ths is about $107 million and that's the amount Oahu residents are paying for the GET rail tax, or about $107 per person.  Accordingly,  $40 (per the article) is what is seen and $67 (the difference) is "baked in."