ok, but you must define, what is a flop. Nintendo Labo is a really niche thing, so i dont think it is expected to sell that much. Nintendo is keeping iut really separate from their main line of games, that's why you will never see a nintendo labo peripheral for a mainstream game. Price wise, it's not that much really. Clearly you never bougth kids toys lately if you think the thing is overprice. a small lego set is around 50$ in canada. heck, last week i went to a disney on ice show, and for 65$ i got two mugs, a cheap plastic crown, cotton candy and a popcorn. my 89$ invested in the variety kit will get me much more for my money...
But, especially with the nintendo garage, which allow you to create your own labo contraptions, and program different things, it migth get the attention of schools at some point. I think it might be the poiint of the thing actually.
and remember that the target audience is not all switch owners., i preorder mine, because i have two kids that i hope will be thrill to build and draw on the thing, but i wouldnt have order it just to myself.
So prediction wise, i say it will sell less than a million, by the end of the year i expectg around 500k units, but i dont think nintendo will see that number as a flop.