From the story on the link you would only have to pay if you want your post to have priority. They aren't making enoough on advertisers so this is a way to send you post to the top. So essentially the companies will priority their posts and the unpaid friends will be the posts at the bottom unless they pay too.
It reminds me of the postal situation. Businesses send out high volume of mail so they get discounts because they bring them in zip code order. A person mailing one little envelope pays full price because it has to be scanned. And our mail box is full of offers we didn't even request and a catalogue from every one we ever submitted an order to. Some catalog companies send me their catalog every 2 or 3 weeks, with not that much new if anything new.
However, if Facebook starts charging even a penny a post, or a fee to move your post so it can be seen above a billion company posts I will be dropping it. How can a company with their income not be making money?