I am referring to the people who buy Rebels, not cellphones, which is about the same price point for a new release. I know that at the moment Rebels are cheaper than that, but they are due for an update. On first release a Tni body with the standard kit lens costs about $100-200 more than the RX100.
Most folk who buy those cameras only use the 18-55mm zoom that comes with the kit, they don't buy additional lenses. The camera is perfectly functional with that lens for most purposes, which is the standard you would use for a compact travel camera.
Its a matter of opinion, the 24-70mm FF equivalent lens on the Sony is closer to a 15-43.5 mm lens on a Rebel. At least, the Rebel covers the standard 85mm FF equivalent portrait focal length.
I'd not be happy just taking my 24-70mmL with me as a vacation lens or walk around lens.
There is a huge market for those 18-135, 18-200, and 18-270, etc super zooms. That's because they are good for vacations and cover a wide range of circumstances, even though they may be a compromise quality wise, they fly off the shelves. Canon has stated in some recent interviews that the superzoom bodies are a bright spot in their sales, because the standard focal lengths are covered by camera phones. Certainly, a lot of users never upgrade their 18-55 lenses, but many of them take a superzoom point and shoot on vacation.
That's also why so many users come here to ask about getting something better to use for their vacation.
If a 24-70mm focal length range is all that you need, that's great, but one size does not fit all, and a buyer needs to consider this before plunking down $800.