Budget the government petition fees from the USCIS fee schedule, the cost of preparing the specialized-knowledge evidence, translation of French technical records, and the vendor contract review. Premium processing is optional and does not improve the case.
The evidence file is where the money is earned
Form I-129 fees, the fraud-prevention fee and any applicable surcharges are published in the USCIS fee schedule and should be read at filing time rather than assumed. The larger cost in an L-1B is professional time spent turning a control-system change log and internal design notes into an explanation an adjudicator without engineering training can follow, which is where most specialized-knowledge petitions succeed or fail. French technical documents require certified translations under USCIS rules, and only the relevant pages need translating, so select them before ordering.
The vendor contract should be reviewed for the offsite rule before filing; adding a clause confirming the company's supervision is cheaper than answering a request for evidence later. If the U.S. plant is a new office, add the lease and business plan.
Relocation, housing and the spouse's business set-up are personal or corporate costs outside the immigration budget and should be tracked separately.