When you deal with the web, almost nothing is hidden. The browsers (and some extensions) have access to just about everything on screen and off. Anyone browsing a site or app can inspect the contents and even modify it. That last part could be key.
TechPowerUp got their hands on a screenshot of developer tools inspecting the Newegg website. A few elements are hidden on the right hand side within the "Coming Soon" container. One element, id of "singleFinalPrice", is set "visibility: hidden;" with a price as its contents. In the TechPowerUp screenshot, this price is listed as "729.99" USD.
Of course, good journalism is confirming this yourself. As of the time I checked, this value is listed as "9999.99" USD. This means either one of two things: Newegg changed their value to a placeholder after the leak was discovered or the source of TechPowerUp's screenshot used those same developer tools to modify the content. It is actually a remarkably easy thing to do… here I change the value to 99 cents by right clicking on the element and modifying the HTML.
No, the R9 290X is not 99 cents.
So I would be careful to take these screenshots with a grain of salt if we only have access to one source. That said, $729.99 does sound like a reasonable price point for AMD to release a Titan-competitor at. Of course, that is exactly what a hoaxer would want.
But, as it stands right now, I would not get your hopes up. An MSRP of ~$699-$749 USD sounds legitimate but we do not have even a second source, at the moment, to confirm that. Still, this might be something our readers would like to know.