If you look at your content and you notice that on average a content page earns $100/year from the adsense/affiliate/cpm/etc. Then it probably makes sense to to hire a writer for $80/article.
Spend $80.00 to make $20.00..!
What..work on a gross margin of only 25% !
Flippin' burgers is more attractive than that..
If you can't make a minimum of 500% ( and a 1000% and upwards is much better as a margin ) over your outlay, then it really isn't worth the headache, you need to be more creative, inventive, or find another niche(s)..
That is without even getting into the "did the writer I hired on X platform/site, really write the article, or did they just copy, spin it, and am I gonna get slammed by the search engines for dupe content and maybe even an irate original owner, or their lawyer, of the text "...and yes you can "check" the text when delivered..
But that takes time..and what is your time worth again..?
Outsourcing, unless it is for code writintg ( and even then you need to be able to understand what you get back ) is a way to expose yourself to a potential world of hurt..and for 25% margins ..!