Their articles ae probably spinner articles or they combining similar contents somehow. However they will not become copy scaped.
Obviously they use Find and Replace. Plus aren't there programs that jumble the content up? You would think that would be pretty easy to do on your own... even in 15 minutes.
Guessed that they would be a team of writers who could do that in a short period of time. However, I think a couple of hours would be fine - 1/2. Afterall, it's only 4,000 - 5,000 words in total and if they're all on topic or def linked through LSI, then I wouldn't find it that difficult. Under an hour would be a push though. BUT - as marketjunction said, if it's what you want and pay for does it actually matter? Afterall, if I use someone else to write an article for me I usually rewrite and optimize it so that it won't be a worthless piece of junk.
I second that Denise, it's called copy from somewhere else and give it to you hoping you never find out!