In chronological age, I was about five years older than she, but while my active mind could contemplate the philosophical implications of the meaning of equality, she did not even have enough intelligence to achieve toilet training. Yet it was clear to me that on the level of basic humanity, we were equal. It means that we are all equal in the eyes of our Creator. The concept of equality does not refer to people's intelligence, abilities, or accomplishments. Those are external conditions.
Equality refers to a person's essential humanity.
On that level, we are indeed all equal. It is the same way with mitzvohs . Dollar for dollar, the wealthy man gives more. It would be foolish to think so. The value of the wealthy man's tzedaka is that he uses his wealth toward good, rather than selfish, ends.