The Xbox One isn't a cheap console, I think we can all agree on that. Chances are it would be a lot cheaper without the necessity for a Kinect 2 camera that you have to buy with each bundle, but hey, that aside: if you take into account inflation, there were some much more expensive consoles in the history of gaming.
While historically, the most expensive ones come from the early 90s and even the late 70s, you only need go back to the start of the current generation to see one of the worst culprits. The PS3 was $600 at launch. In today's money that's just under $700. Comparatively, the Xbox One's $499 price tag doesn't seem so bad.
And the PS4 even less so, at just $399.
If you want to talk real ridiculous prices though, how about the 3DO, released in 1993? That was $700 back then, which is the equivalent of over $1,100 today. The Neo Geo was only a few bucks less back in 1991.
If you want to talk cheapest however, Nintendo steals the show with Gamecube, at just $200 at launch and $264 in today's money. The Wii wasn't far behind either.
Technically, the chart [Thanks CVG] has the Sega 32X as the cheapest console ever, but that was a lacklustre add-on for the Megadrive/Genesis. It would be like giving the award for best console to the N64 memory pack.