A gift to the U.S. government and a processing fee, in the amounts published on the official program page. Confirm both on the day the decision is made, since they have changed before.
Count the tax on getting the money there
The two payments behave differently and should be budgeted separately. The official FAQ identifies the processing charge as nonrefundable. The gift is an unrestricted transfer to the U.S. government: it buys no asset and earns no return. Establish from the current official material which amount applies to each applicant and family member and what happens if one person is not approved. Then add the cost of obtaining liquidity: where capital is held in shares acquired through options, tax on exercise and sale can be a substantial part of the total. Around all of that sit ordinary professional and document costs.
Read the official terms and record the date, choose the individual or corporate framework, settle who is joining, obtain legal advice on admissibility and category eligibility, pay the processing fee, complete vetting, and only then is the gift payable. Anyone comparing this framework with an investment category should compare total outlay together with recoverability, since money given and money invested are not equivalent expenditures however similar the headline numbers appear.