If it's for writing small news bits, it can be. Let's say you're a total expert with using GMail and you have to write a couple of posts linking to GMail news, the occasional tip, etc, each day - you can probably bash short posts out in no time.
You have the many hundreds of hours invested in actually become the expert in the first place, but I doubt anyone becomes an expert so they can write $50 a pop pieces - so that cash is extra value, not a payback for the time you spent learning (as is the case with a professional's fees).
Put another way, how much do you expect to earn per hour for this sort of work? How long does it take you to write an informative 300 words?
However, if they don't have to put their names on the article then you're right, it is a good deal.