This is a good question. I would say that beauty pageants are exploitative for several reasons.
First, it emphasizes a certain type of beauty. No matter what people say all the contestants are skinny and have a certain look to them. Hence, they are narrowly defining beauty. What about the rest of the culture, who looks different? Moreover, it is all for public consumption.
Second, all pageants are superficial. Of course, there is a talent and interview portion, but it is shallow. So, it is all about the external. From this perspective, we are exploiting their external appearance.
Third, think of what this pageant culture is doing to children. Little girls want to confirm to an unhealthy ideal. This is exploiting young minds of what beauty is.
Finally, it does not matter that these contestants are wiling. The worst time of injustice, according to Bourdieu, is when those in power made the subjugated abettors of their own subjugation.
beauty pageants are not exploitative because in the world every area or field could be exploitative if person choose worng way of success. beauty pageants give not only stage of physical beauty but also it show menally intelligence and intellectuality.
and it show standard patterns of beauty, it show that black skin is beauty too. it present woman empowerment and she is become roll modal for society.