The employer files Form I-129 with the L supplement and pays the fees published in the USCIS fee schedule, Form G-1055, with optional premium processing where the timing has to be certain. Legal drafting and the retrieval of corporate records are usually the larger line items.
The filing fee is rarely the expensive part
Because amounts change, the fee schedule is the only source worth relying on, and any figure quoted second-hand should be checked against it before a budget is approved. What surrounds those fees is more substantial. An L-1A petition for a group with a holding structure requires corporate records assembled from more than one jurisdiction, sometimes involving registry searches and certified copies.
Counsel then has to draft a description of managerial or executive capacity that survives scrutiny, which takes time proportional to how unclear the organizational chart is. A request for further evidence, which is common where capacity is asserted rather than demonstrated, adds another round of both. Employers who invest in a clean chart and a precise functional description at the start generally spend less overall than those who file quickly and answer questions later.