I have been mentioning this from the start but from a different perspective. Sasuke never had any chakra problems, because being an Uchiha, he's naturally blessed with high chakra reserves and a powerful chakra. What you are seeing is EMS greatly reducing the stress on his body. And this is no exaggeration.
Just look at these images:
1-
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and
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- His eye is bleeding very profusely after using Amatersu.
2 - - He's saying that his every cell is feeling the pain, and let's face it, it clearly shows. Prolonged usage of MS sussano - level 3 - put an immense stress on his body:
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Then look at this:
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- A complete sussano and Amatersu. Not only there is no bleeding from the eyes, but he is walking as if nothing happened.
I noticed that he did bleed when he used a level 4 sussano:
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While here inside level 4 sussano, and the enton Gatling gun, he is standing pretty casually:
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Looking at all of these images, it's safe to assume that when Sasuke utilizes EMS Sussano with any other right or left eye EMS techniques, he feels little to no stress from the usage. This means, that the chakra consumption is exponentially reduced for EMS.