I'm a writer, mostly these days. Here's some things to consider. You guys are talking about hiring a "writer" who, presumably you can give a topic, and receive back a reasonable quality article of appropriate length. What you will end up with is an article on the topic that will look like and be a rehash of what the writer can quickly find for background material, which has also been produced that way.
If that's ok, pay as little as you can and your criteria should be low.
However, if you want content that will make people go "Wow, I never thought of that", and be good enough to compete against the type of material I write about which I know a great deal, you need to hire subject matter experts who are also good writers. These folks do NOT grow on trees.
And, they have better things to do than write for blogs nobody has heard about, not the least of which is writing for their own platforms. Price? If someone wanted me to write something completely original, crafted, etc, I wouldn't even consider it for under a hundred and probably $150.00 would be barely ok, IF the topic fell within my areas of expertise. I dunno. Probably wouldn`t do it regardless.
Ultimately it depends on what you want: SEO text. A basic article just like most every article on the topic (you can get those free at the article sites), or something that will tell people they NEED to return to you because your site has something important to say.