Attractiveness–beauty–correlates with success. The study I gave you does not break out which features trigger favorable responses, but I can assure you that breasts are high on the list. Looking around this board might help you research that.
You have grown confused about whether or not I think breast size is the primary feature for attractiveness or success. This certainly varies by individuals making an evaluation. WRT attractiveness, I don’t personally think breast size beats out a pretty face, and perhaps not even an otherwise nice figure (legs; hips; etc). So a chubby, unkempt, facially unattractive woman should probably not spend her first focus on getting a shaplier bustline. I think I can say that for me personally, intelligence is far and away the most important driver for success, and personality second. For me, physical beauty is an introductory point of interest that rapidly recedes if intelligence and personality are deficient.
With a flat-chested woman who is otherwise attractive, though, the equation becomes more interesting. Should I spend 10,000 dollars on larger breasts, or should I spend it getting 10,000 worth of education?
10K doesn’t buy very much education. It will buy a shapely chest. Were I put in the situation of advising such a person–and if I thought her ego could handle it–I’d tell her the augmentation is a better fiscal bet. I think this is the obverse of the postulate underneath the concept implied in the OP. You are essentially balancing the value of breast size against the value of intelligence. Both help with success. Neither is always necessary. Neither is ever sufficient. Trading a little intelligence for larger breasts is simply a variant on the tack of trading a little education for larger breasts.
Now if you throw intelligence into the mix, along with personality, it’s a different question. Should an attractive, intelligent, personable young woman ask me what to do with a 10K investment, my answer would be to spend it toward education, on the assumption that an initial investment in education would be incrementally rewarded because an intelligent individual will stand out and will be more likely to have opportunities created in recognition of initial success related to her intelligence.
If you have to choose (for the point of this exercise) between a shapely figure and a small amount of education (as if those two could be teased out in isolation) for an otherwise attractive woman, I maintain that larger breasts might well be the better financial spend. YMMV, but I am not personally surprised at the several hundred thousand women who have elective augmentation mammoplasty every year in the US, although as a physician I’ve occasionally been startled at high how it ranks for younger women who I might have thought would have better spent their limited funds elsewhere. Must be Cosmo’s fault (or people like me giving bad advice).