As with anything on Fiverr, if they have done a lot of work and have good feedback it's not a lot to spend.
I really can't work out how they could do it at the price though. Even for kids it would be low pay (maybe they are Chinese kids?)
At the US minimum wage, which would be very low for skilled work, I'd struggle to do a first pass of a novel. Reading through to identify any areas of special formatting and looking for issues/inconsistencies within the original document that are likely to cause issues in the final document takes time.
Add in the formatting itself, quality reviews on different devices, giving the client a chance to feedback and ask for changes etc. and you've got a wage that's approaching unskilled northern chinese levels. Makes the mind boggle
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