I think that's a compelling reason to believe this to be a fake. The amount of hardware needed to run such a resolution is substantial and I don't think people would want to pay that kind of money for a Chromebook right now. Personally, I would have to be assured that I could run a fuller operating system on it if I were going to spend that kind of money.
However, even if it is real, it seems like it would be much closer to a Retina MacBook Pro than any current Chromebook. It seems unreasonable to think that Google would be able to put out such a device with such a display that is like the current Chromebooks in hardware or price. I know that a lot of us would love someone to unseat Intel, but we've seen how demanding Retina resolutions are and how even processors many times more powerful can struggle to meet the task.