Using places like Langbaan and Pok Pok as proof that Sen Yai should have no problem charging $11 for noodles is a mistake.  Langbaan and Pok Pok are black swans.  You can't use them as indicators of what's normal.  Pok Pok came on the scene with perfect timing, moving from cart to restaurant and garnering tons of press both local and national.  I see more Ubers in front of that place than many downtown steakhouses.  A good number of their customers go there to say they went to Pok Pok, not because they have a palate that begs for traditional and unusual Thai dishes.  Same with Langbaan (which has like 10 seats).

What they should have done was call it Pok Pok Noodle House to get some of those foodies to follow the brand in the door.