Those stats and statements are made by Rumya S. Putcha, Ph.D., in her article "The Trouble With Yoga."
Here stats are correct as is her concern. This is changing. Little by little people with limited discretionary income and people of color are making their way to yoga studios. Many centers don't turn people away due to lack of funds by offering work exchange opportunities, discounted class passes and even scholarships. Yet, there is more which needs to be done especially in finding effective ways of reaching under-served populations.