The government fees are listed in the USCIS fee schedule and are paid by the petitioning employer. The larger cost is usually staff time to assemble internal technical evidence, plus any premium-processing fee and the relocation package the company chooses to offer.
The expensive part is documentation, not the fee
The fee schedule sets the I-129 base charge and any additional statutory fees for L petitions, and the employer may add premium processing for a faster decision. Those figures should be checked on the current G-1055 rather than assumed from a previous case. What companies underestimate is the internal effort.
Proving specialized knowledge requires engineers or technical managers to locate dated design records, write staffing memos and review the support letter for accuracy; a small Québec firm may spend days of senior time doing so. Hypothetical example: a Lac-Beauport-based laboratory instrumentation firm assumes the petition will cost little more than the fee, then discovers that its proprietary calibration procedure was never formally documented and must be written up before it can be evidenced. The relocation package, temporary housing and any tax equalization are business decisions outside the petition; record them in the employment agreement, and do not describe them in the immigration file as if they proved eligibility.