Government charges depend on the route and are published in the USCIS fee schedule. The larger controllable costs are evidentiary: credential assessments, licensing applications and obtaining corporate or employment records.
Most of the spending is on proof
Hypothetical example: It helps to divide costs into those set by government and those created by the state of the applicant's records. The first are published and should be read from the official fee schedule rather than from any summary, since amounts and options change. The second are the ones a household influences.
An equivalency assessment of a foreign degree, a state licensing application, obtaining certified copies of civil documents, and the accounting or legal work needed to bring a family company's corporate record up to date all cost money and time. A Cavan Monaghan applicant whose paperwork is in order may spend very little; one whose credentials need assessment and whose corporate records need reconstruction may spend considerably more. Estimating honestly at the start prevents the household from committing to a plan whose real cost only becomes visible halfway through.