Nuendo is aimed at post-production, where you need different features. The ADR taker, just by itself, would be worth the price of Nuendo.
Steinberg like to think of Cubase as the flagship music DAW and Nuendo as the flagship post DAW, and both have exclusive features; but you can add Cubase tools to Nuendo using the NEK.
There are features in Nuendo that are as useful to music production as they are to post, such as AAF import/export, the advanced crossfade editor, and (arguably) multiple marker tracks. This makes the notion that Cubase is the flagship music DAW questionable.