Who gets money from heart/breast cancer walks?

Charities. Very good question and one you should be asking the organizations. The questions to ask: how much of every dollar collected is for overhead, for patient related literature produced, for designated research facilities [and which ones and is it a grant that is restricted to breast cancer research or not]. Do your research, some 'charities' are supporting themselves.....
The heart walks are. Sponsored by the american heart association; the race (not walk) for the cure is a susan g komen foundation activity. I do not know what aha does with their money; komen sponsors many women's activities and some research, but has its own board decide how to disburse collections.