it's not about how many videos you have but about how much you promote and also how many followers you have on camsites and all. the girls that make bank on MV have tons of followers on MFC or CB and make bank there as well.
You have to promote Manyvids like crazy to make a great income on there. However, if you are not a popular cam model on CB or MFC then it will be super hard. Plus, their customer base is super vanilla.