expensive paperweight

An object that may have had an original purpose (usually electronic devices) or a concept model of something else, but in any case unable to serve its intended purpose except as a display item or a paperweight
Since many of these paperweights, especially those of the old electronics category, required a larger investment at its initial purchase, these paperweights become expensive, hence, the "expensive paperweight"

I found an old ipod in my uncle's basement, but it doesn't even work anymore so now it's just an expensive paperweight!

Is that a BlackBerry?
It WAS a BlackBerry, now it's just an expensive paperweight!

Whoa is that seriously a holographic infrared keyboard?
Nope, this is just the concept model for a holographic infrared keyboard that got rejected during the pitch... So now it's just an expensive paperweight!