Hi,
@Quit925today. Being a native English-speaking writer does not always guarantee desirable writing style.
A non-native English-speaking niche writer can outperform an English-speaking general writer.
On the other hand, I agree that there are collaquials that are best used and interpreted appropriately by native English-speaking writers.
There are pros and cons. Like what the other BHW has said, you need to try your best to strike a good price-to-quality ratio.
I suggest that you look or ask for the content provider's customer reviews. The reviews must be have a timestamp so you will know if that provider actively receives testimonials from his or her customers or not. Fave reviews do not have a timestamp and the reviewer's identity (e.g. name, website) usually.
Also, interview the content provider via chat on Skype. You will see the provider's grammar and writing style through chat.
Finally, do not ask for the "standard price" per article or per word because there is no such thing as a standard price for someone else's value for his or her time and talent. Some are willing to work for free. Some put a price tag that it seems like they don't want to sell their service anymore because of their higher-than-expected rates.
The best thing you can do is to check the Marketplace section of the forum, find the threads with the most number of customer reviews, and try the service of the top 3 to 5 providers you've ranked. That's just it.
Satisfaction on someone else's service is personal. You can't always take someone else's review on some else's service as an absolute barometer. Some clients can be easily satisfied while some cannot be satisfied with anything on this planet.
You'll never know what you're getting or losing unless you try it for yourself.
I hope that helps.
Jaycee