I have to agree with you, they are damn expensive.
Their strategy about it is not insane, however, because I'm afraid those spinner packs will sell like hotcakes nonetheless. Remember, their job is to make as much money as they can, not making money of exactly you or me.
They don't greatly appeal to me because of - yeah, you've guessed it - the high price and the cheap, cheap plastic which I hate! But I'm nothing in comparison to the big market out there. Why should people who are used to buying Magic the Gathering decks for 13 euros refrain from buying a Lego minifig, a spinner and some cards for 10 euros? NinjaGo is combining two big interests of many, many children and that's why I expect that the "game-based" sets will be a success for TLG.