"Where does one go to buy things like a refurbished 5 megapixel camera on the cheap, if that's all one needs?"
I don't know of any dependable place.
The problem scenario goes like this. Customer buys a $400 camera from a big box store. Customer drops it or does something unexpected to it, and then it doesn't work exactly right all the time. Sometimes it is only that the customer did some special user setting, because he was too stupid to understand, and nobody quite knows how to put it back to "stock" condition. Customer brings it back to the store, and they settle with another camera of some type. Now, what is that store going to do with the used camera? If it was a hugely expensive camera, the manufacturer probably has a factory repair center that can refurbish it. More typically with a less-expensive model, the used camera is sent in, and a substitute camera is sent back out for a fee. In that case, the used camera is probably decent since it is the factory repair center that blessed it. However, sometimes everybody is too cheap to get the factory repair job done on it, so the store guy simply tries a couple of snapshots, and it seems to be OK at that cursory level, and then the camera is placed back into packaging and sold at a deep discount, sold as an "open box." In fact, it should be sold as "used."
So, when you are buying a used camera, most of the time you really don't know what you are getting. Lots of people will buy used cameras only from friends whom they trust.