Beyond the government charges published in Form G-1055 and any premium processing, budget for the possibility of a detailed request for evidence. Specialized-knowledge petitions attract them more often than managerial ones, and answering one properly means producing internal documentation the company has never had to package before.
The second round is where this category gets expensive
Filing costs are published and predictable; the variance in an L-1B budget comes from adjudication. A request for evidence on specialized knowledge typically asks for exactly the material a thin petition omitted: what the knowledge consists of, how it was acquired, how many others hold it, and why the position requires it. Assembling that under a response deadline is more expensive than assembling it at the outset, because it pulls senior technical staff away from operations at short notice and gives counsel little room to shape it.
Where a customer-site placement is involved, the request will usually also probe supervision and control, and the answer depends on contracts that may need renegotiating rather than merely producing. The cheapest version of this case is the one filed complete. The most expensive is the one filed thin, refused, and then refiled with the evidence that should have accompanied it.