Show payroll in the business operating budget, separate from government and professional immigration costs. It may support the new-office plan, but paying salaries is not an L-1A filing fee or a fixed statutory investment requirement.
Fund the plan you describe
Explain how the company can meet recruitment and operating commitments rather than selecting arbitrary staffing costs to make the petition look stronger. Separately budget petition preparation, current filing charges, dependent procedures and any optional premium processing. Ask whether professional fees include reviewing financial and staffing assumptions together.
A cheaper petition cannot compensate for an unfunded operating plan. Planned payroll is a business cost and belongs in the operating budget rather than in an immigration budget, but the plan is not credible unless the business can actually fund it. Model the payroll commitment month by month against available funding, including the employer costs that sit on top of salary.
Then keep the immigration charges separate: government fees depending on the petitioner and filing type, any supplemental fee whose application depends on the employer's characteristics, dependent applications and any optional processing. Where the funding for the hires comes from a parent, document the mechanism. The general principle is that the plan you describe should be the plan you have funded, since a hiring schedule the business cannot pay for will be tested against the accounts at the extension stage.