At least the first PV costed 40 million yen, 2~4 times as much as a typical TV anime episode.
Sunrise 8th studio made Idolm@star into a mecha anime once, and now is producing a true idol anime. I have to say I'm full of deep emotions.
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Are you going to say "budget"? Wait! Is your point really related to budget? Isn't it time or style?
Simply put, production time is consistency, and budget is framerate.
Even poor animation is costlier than a high-quality still shot.