How did masturbation originate and why do people do it? Is it an innate disposition with which God created us? And what should a person do in light of the high cost of marriage?

Masturbation is not part of human nature (fitra); rather, fitra is to expend desire in what Allah has permitted, such as with one's spouse. The statement that all humans practice it is incorrect, as many believers are chaste. Allah Almighty marvels at the youth who has no inclination towards worldly desires, and his not falling into them is among the wondrous things, because human nature calls the youth to desires. The difficulty in getting married does not permit committing what is unlawful; instead, it is a call for patience and seeking reward from Allah.