How much do I charge to re-write the content on someone's website?

[Jake]

I'm only familiar with per article pricing, assuming an article is about 500 words, a basic grade original article cam be bought for around $3, rewriting is generally considered a lower skill than original articles so I would imagine $1.50 to $2 per article might apply, these figures are for articles written primarily to gain search engine ranking. Quality authority sites pay more like $10 - $75 for magazine quality articles by respected authors.

You can review the project cost on sites like odesk.com, freelancer.com that may give you some reference figures.

Here are a couple of example article brokers that pay for better quality original works
constant-content.com, textbroker.com, thecontentauthority.com