Making 2D art is a huge factor imo. It's expensive as hell.
It's also extremely time consuming, even for skilled artists.
It's just more efficient to use 3D.
Just having this made cost me 45$, and it's not even "complete".
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This cost 130$ (and the artist literally disappeared and refused to answer messages, so I'm lucky it was even sent to me):
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My first loves are pixel art games and 2D though. Honestly, there are so many draw backs to working with artists that I don't think I ever will again if I can help it. That's not to say all artists are bad people, but they have a reputation of being difficult to work with for a reason. All artists seem to have one quality in common, they are emotional which leads to great degrees of self expression. On the flip side, this also makes them fickle. That means the slightest thing will often turn them off to working with you. The irony is, if you're paying them - managing their mood and motivation should not be a factor in whether they can complete their work.
But, it usually is.
In the case of Heavenly Peaks, I paid the artist his asked rates + 20% project profits for a lifetime. It still wasn't enough.
P.S.
I will have my own anime one day.