Salon charged me more because I have ethnic hair ?? ?

I went to a hair school to get my hair flat ironed and they said b/c I have ethnic hair it will cost more....but the thing is I have relaxed hair so it's not as course...are they wrong or right??

Could it be that it still takes a little extra time, or they have to use products that they may not have to otherwise? All being equal, I'd say it was not cool. But, if they have to spend more time doing your hair, or use expensive products to protect it, then it sounds all right to me.