The areas around Jakarta and Bandung are not dirt poor backwaters; there are literally millions of middle class Indonesians able to afford such prices, and more every year as the country develops. Also, having high speed rail tickets as low as $16, which the article admits is “comparable” to other options, is already a huge feat!
This simply sounds like the writer is casting around for any negative views they can find, in order to shape a narrative. You can unearth such grousing about any infrastructure project, no matter how worthy, if you ask enough people.