The Finasteride 1mg tablet you can buy at For Him is the FDA-approved generic equivalent of Propecia. The only reason people pay more for branded names is that they feel more comfortable with a brand name.
A company that makes a branded drug invests in research and development, so they usually charge more for their branded product. When the FDA allows generic versions of a brand drug to be sold, they require that the generic drugs have the same quality, safety, and effectiveness as the brand drug. Because of the For Hims legit reputation, you can trust their generic versions.