Petition fees are published in the USCIS fee schedule and are payable by the filing date. The larger and earlier costs are usually corporate: entity formation, premises and the first hires.
The company spends before it files
Hypothetical example: A new U.S. arm incurs its real expenditure ahead of the immigration filing, not after it. Incorporating the subsidiary, securing premises, capitalising the entity and making early hires all have to be far enough along for the petition to describe them truthfully, which means the money moves first.
The government filing fees are set out in the USCIS fee schedule and should be read there rather than taken from any summary, since amounts and premium options change. What a Selwyn business can control is the order: spend on what the evidence requires, in the sequence the evidence requires it, and avoid front-loading expenditure on parts of the plan that a first-year new-office approval does not yet need. Mapping each payment to the requirement it supports also makes the eventual extension file easier to assemble.