Well, From my mind and experience in online services there should be cost 10$ or more for around 5000-word essay writing service. I mentioned before the price depends on the quality, So there may be also 100$ for 5000 words.
You may try Essaychief to write an essay by professional essay writers. They are a pretty good essay writing provider company. Their writers are good and will give you the best service and the fact is their price range is also good and fair. From my research I got some pretty good reviews about essaychief, So I think you will get the best professional writers from them.