NBTS -- Worth $$??

Is NBPTS certification worth what some states and systems are paying for it?  Does it really identify the most effective teachers.  Not according to two educations psychologists who've done value-added studies:

Their analysis shows the top 10 percent of ordinary classroom teachers in North Carolina--those without national certification--produce student achievement gains 10 to 20 times larger than those produced by teachers with NBPTS certification. Under the uniform salary scale, these top teachers receive no additional pay for their exceptional work.

NC is paying $7,500 per year to NBPTS-certified teachers!