According to a Bill of Materials report (re: IHS iSuppli Research, March 2012), the camera component of the iPad3 costs only US$12.35. On the iPad2, it costs even less; US$4.10. Of course, I am sure this only refers to the lens and sensor components. The other costs of the iPad3 : display ($87), touchscreen ($40), processor ($23), battery ($32), and so on. But my point is, it only costs $12.35 for Apple to include a really good camera in the iPad3. No doubt it also costs Samsung and others more or less the same amount to include a good camera into the tablet or smartphone.
As for the quality of the images taken by a high end smartphones (i.e. iPhone, Samsung Galaxy, Sony Xperia, etc), they are now comparable to images taken by most point and shoot cameras. Image quality is no longer the differentiator. The web-publishing features and carry-anywhere convenience of a smartphone is what counterbalances the advantages of a faster turn-on time, longer battery life and the zoom lens in a P&S (point-and-shoot) camera. Even video shooting on a smartphone has caught up with the P&S world.
To underscore the coming of age of "iphoneography", the Australian Photographic Society is launching its inaugural Mobile Phone Photography Showcase in July 2013.
So if you ask me today what is the cheapest good camera to buy, I might tell you to look no further than to upgrade your smartphone or tablet. Or, if you are an Apple aficionado, your iPod, iPhone or iPad. The only caveat is, what is your image making goal?