http://www.wmdportal.com/wp-content/uploads/2012/02/WMD_Overview_160212.pdf
This is the original overview pitch pdf for their crowdfunding portal announcing Project CARS as the first project back in 2012. Check out pages 16, 19, 28, and 36. Especially page 28.
Now, by the same token, can't PS3/360 owners be just as mad? Or does that not count because it still came to a PlayStation and Xbox console?
In the case of Project Cars it's actually an investment. You will actually get the money you invested back and then some profit on top.
Which makes the complaints even more ridiculous:
You get to keep a PC copy
You get your money back
You get profit on it, even
I invested like $12 or something for an early build years ago, but they later said I'd only get a discount on the final game or something, so I didn't bother.