Color me highly skeptical. I'm sure there's a financial incentive here, in addition to the racial/religious expression of hatred. But I sincerely doubt there's any such number involved for "each child."
I'll bet wherever the number originated, it said "up to" rather than "each," and I'd be skeptical of even that number.
The numbers just don't work.
For a girl to gross $300,000/year, assuming a five-day week, she'd have to average $6000/week, $1200/day.
I recommend the book Freakonomics, which carefully examined the economics of prostitution in USA. Turns out there are two varieties, one of which is simple street prostitution. Low rent sex for money. Prices are surprisingly low, with hookers averaging gross income of $25 to $35 per hour, largely because of competition that doesn't charge anything for its "services." Classic dinner and movie date is a lot more expensive than just hiring a street hooker. 40 hour weeks, $35/hour works out to a max of $70,000/year.
The other main type of prostitution is the type Charlie Sheen and Spitzer patronized. It's MUCH more profitable. But as the book points out, they aren't really selling sex as such, they're selling the trophy wife fantasy on an hourly basis. The top players in this group might make something like the income described in the article, or even more, but by definition they are model types, not the abused street girls of the story.
The girls in Rotherham were most definitely part of the street version, not the fantasy version. AFAIK, they also seldom if ever "worked" full-time.
IOW, the numbers in the article are bogus. Luckily. If there were such financial incentives to enslaving females, the problem would be a lot worse than it is. Of course, the economics of the market ensure that if these kinds of profits were to be made, the market would soon be flooded with competion, causing prices and profits to drop.
While the math may not work there is no doubt these crimes took place and no doubt about who committed them.
Try them in a court of law and when convicted drag them into the public square a hang them.
If they charged $50 per, a girl could easily bring in $1,200 a day.