Separate the USCIS filing fee and any premium processing charge, both on the G-1055 schedule, from legal fees, corporate document preparation, translations and the U.S. entity's own setup costs. A new office adds lease, payroll and accounting expenses that exist whether or not the petition succeeds.
Budget the petition and the business as two projects
The petition line contains the I-129 fee, the fraud prevention and detection fee, any asylum program fee that applies to the employer's size, and premium processing if the timeline demands it; verify the current amounts on the USCIS fee schedule because they change. Legal fees for a new-office petition are usually higher than for a transfer to an established subsidiary, since the business plan and premises evidence take work. Translations of Québec corporate records and payroll documents add up when the company has a long history.
The business line is different: incorporation or registration in the state, a signed lease, initial payroll, insurance and an accountant who understands cross-border ownership. Keep them apart so the family can see what is sunk if the petition is refused. Ask counsel whether the fee quote includes responding to a request for evidence and preparing the extension, or only the initial filing.