I've been around gaming a very long time, and I'm not sure that I've seen a "major" console depreciate faster than the Xbox One has depreciated in value. It's been about 20 years since I've seen anything like this. The Panasonic 3DO launched for $699.99, and I'm sure by late April 1994, you could find a used one in the classified section of your newspaper for maybe $450 or $400, which is a really huge drop in value.
However, in the 20 years since the 3DO, I can't think of anything that has depreciated as quickly. Also, it's kind of hard to consider the 3DO a "major" system, so you'd probably have to go back even farther.
So, I bought an Xbox One on launch day, and I paid about $517 with tax and everything ( I had a Target red card, so actually got 5 percent off or it would be a bit higher ). I paid $517, and I got an Xbox One system, along with a controller, power supply, Kinect 2.0, etc, etc. No games came with my Xbox One, and I didn't get a second controller.
So now, about 5 months later, I can go to my local Craigslist, and there are people "struggling" to even get $350 for their Xbox One system. Demand has literally fallen off a cliff it seems. The stores are overflowing with stock, and anybody that really, really wanted a Xbox One, has probably already gotten one. If you're in a situation where you are forced to sell off your Xbox One for whatever reason, you're going to take a HUGE loss on the thing unfortunately.
I saw this one guy selling an Xbox One system, and he was including two games, and an extra controller, and he was trying to get $350 for the thing. That's with 2 games and an extra controller ! So, the one that I bought for $517, which only includes the one controller, and doesn't include any games, must be worth even less than $350. In fact, if you were in a desperate situation, and had to sell your Xbox One for whatever reason, and you didn't have any extra controllers or games, you're probably looking at $300 in the clear, which is downright laughable, considering this thing is only like 5 months old. To go from having a $500 value to having a $300 value in 5 months, is almost unfathomable. Yet, that is exactly what is going on with the Xbox One. Sure, the 3DO had a similar decline, but 3DO wasn't the market leading console in the previous generation. 3DO was a bit player at the time. Probably given less of a chance of success than even TTi's TurboDuo or the Atari Jaguar. So, you might have to consider the 3DO like the 4th or 5th competitor at the time. Microsoft is one of the big 3 right now, and their number one platform has lost almost half of it's value on the secondary market, in a mere 5 months.