Milky Way Manager Achieves 9 Stars!!!

Since all of Manager Milky Way's Sugar-Lune abilities are unlocked, and it seems like the final promotion to 10 stars can be achieved through the permanent gacha + continuously distributed SSR selector tickets instead of the pickup gacha, I intentionally saved my resources without spending them all, in order to save up for the next pickup SSR support cookie. However, a question like this might arise, right? If you stop at 9 stars to save resources, wouldn't it be more cost-effective to stop at 8 stars, right before the Sugar-Lune additional effects are unlocked right before 9 stars which boost skill stats, since the upgrade from 7 to 8 stars feels much more impactful than the upgrade from 8 to 9 stars? The reason I didn't stop at the cost-effective 8-star upgrade and promoted Manager Milky Way to 9 stars is because Unlike the permanent gacha where it's hard to get Manager Milky Way because the rates are the same as SSR cookies, I felt it would be better to do it during the current Milky Way pickup gacha period, where you have a high chance of getting Manager Milky Way, so I promoted Manager Milky Way to 9 stars.