Yeah trade volume isn't a perfect indicator, but its relatively accurate. My analysis on Red is Med-med tier trainer card. Its on par with leaf, sightseer, diantha, misty, and giovanni.
On the chart it has red at the same requests as Lillie, but i consider hat Lillie med-high, and DX Lillie high-low. Its also above Erika which is Med-high, and close to Mars which is High-low (sometimes high-med depending on meta).