How much to charge per 250 words?

Hi!

How much should I charge per page of 250 words?

Should the rates be different for UK and USA students?

I have Indian writers in my team. But the writers write excellent papers and dissertations. However, there is some problem in their English language. The students get very good remarks from the teachers despite that.

Sometimes the instructions appear unclear or the writers don't get the 100% of the instructions other than that they produce really very good work. We work for some of the top UK companies.

Thank you!:)