I watched the video and this seems pretty neat. Don't want to knock it or be negative. He's definitely right that most people's knives are dull – when I use knives in other people's homes I often just want to cry at how dull they are (also: pans – how the hell do so many people have dented damaged pans?) But you really don't need to splurge out €329 to have reasonably sharp knives.

All you need is a sharpening steel and use it once or twice after every usage. Even a cheap knife will last for years while remaining reasonable sharp. Mine was €6 or thereabouts at Tesco two years ago and is more than sharp enough.

Of course more expensive knifes (ultrasonic or not) are better and can hold an edge longer. You can spend more time, effort, and money on making them sharper than just a quick use of a cheap sharpening steel. If you want to spend the extra money: go for it! But for a normal home cook: you can go a long way with consistent use of a €10 sharpening steel.