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V-Tubers are still a niche at least that's what I think but I think Suisei has been one of the few breakthrough to be accepted by the general public so her music is doing pretty good.
Plus she won't do any what the Japs call "AKB commercial law" or something which means to bundle the CD with handshakes/meet n greet tickets so physical copies won't always be super high but digitally she's probably doing amazing.