Looks like you are right. I think you should go to Dumaguete LTO immediately and demand they stop mandatory drug testing. Actually, it doesn't matter much as foreigners who have never had a license aren't supposed to be getting one. If they are refused at the LTO they won't need to get a drug test, will they?
That means losing jobs for the I counted 8 people employed in the <medical> and drug test office. Including the same old lady doctor I saw 3 years ago ( thought her then already close to dead ) still combing her hair and glancing in a mirror, They may be all related to the mayor.
Here's an interesting add on to that: Last time I was at LTO they told me I need glasses next time. So today I went to the eye doc to get glasses. She gave me some for reading and looking at the computer and told me I did not need glasses for distance. In fact, she tried a few different lenses and they each made my vision worse. Then she said the staff at the LTO medical test place are not qualified to give eye exams and don't know what they are doing. Left hand not knowing what the right hand is doing comes to mind.
While driving around in Thailand, somewhere in the Northern part, a couple of years ago, I encountered a check point of Thai police. They asked for the papers, motorbike was rented, so ok, then I showed my International Driver's License (which was already expired), they took a look @the picture and ok again. Why they did not notice the license was expired.............in Thailand the notation of the date is different from many other countries, using the Bhuddist era which is 543 years ahead of the Gregorian year as used in European countries, USA and the Phils. There may be of course still enough Thai policemen around who knows how to convert, so don't try your luck if you want to be safe in stead of sorry.
Just thinking... Maybe you had more drugs to test than your GF, so they charged more. I have been told it costs more to administer drug tests to foreigners because of all the extra questions involved that the female tester has to ask. ie: "Are your married?" "Do you have a girl friend?" "Are you going to marry a pretty Filipina?" "Do you want my phone number? etc......
On this topic, I discovered my US drivers license expired near the end of 2014. I was thinking of going to LTO to see what would happen. Don't need to drive, but I may have to get one of those year long visas. So I need to start the process.
What kind of visa are you on? As far as I know 6 month is as high as tourist visa goes. I think other kinds of visa are usually obtained before you travel to the Philippines.