The employer files and pays the petition charges published in the USCIS fee schedule. The substantial preparation cost is assembling and organising the technical evidence.
Budget for the evidence work, which is where L-1B files fail
Hypothetical example: The government charges are the petition filing fee and, if the company chooses it, premium processing; both are published in the USCIS fee schedule and should be confirmed at filing. What companies routinely underestimate is the work of turning fifteen years of institutional knowledge into a documented case. Someone has to find the original specifications, confirm authorship, redact commercially sensitive material, write the replacement-training comparison and produce a chronology of employment from payroll records.
For a small manufacturer without an internal legal function this is real time from people who are also running the plant. Requests for further evidence are common in L-1B because the specialised-knowledge standard invites scrutiny, so budget for the possibility of a second round. Spending on premium processing before the technical file is complete simply accelerates the arrival of that request.