Get some idea through checking those writers on fiverr. You'll have more idea comparing the freelancers there and how much they write for each article or blog that they write. I don't use that platform so I have no idea about their payment scheme or they allow bitcoin as payment.

But if you've seen some great writers here, you can negotiate on how much they charge. You'll find a lot of great writers in the forum that can help you out with the right pricing and quality works.