you need to produce 250 words per hour to equal the reported avg. Wal-Mart wage of $17.50 per hour (although as he notes, excluding benefits).
So if someone works a 5-hour day at Wal-Mart, they could earn the same amount by typing a 1,250-word article (250x5) for that website. In however long it takes them to do that. 1,250 words is not much — maybe 25-30 sentences or so.