The petitioning employer files and pays the government charges, which are published in the USCIS fee schedule. The overlooked costs are documenting the proprietary process and, for the family, licensing and credential evaluation.
Budget the documentation, not just the filing
Hypothetical example: a Grand Bay-Westfield shop treats the L-1B as a line item equal to the filing fee and is surprised by the total. Government charges depend on which forms are filed and whether faster adjudication is elected, and they should be read from the current fee schedule rather than assumed. The larger and less visible spend is preparing the evidence: engineering time to assemble and redact procedure documents, the owner's time reconstructing training history, and professional review of a specialized-knowledge description that has to be precise to survive.
If the transferee's family is moving, add credential evaluation and licensing fees for the spouse, which the employer may or may not cover. Settle in writing before the move who pays what, including any repayment clause if he leaves early, because such clauses have their own employment-law consequences on both sides of the border.