Filing charges confirmed against the current USCIS fee schedule, plus the professional cost of assembling process evidence that usually does not exist in a presentable form. Expect legal review of the joint venture agreement and internal time spent locating protocols, revision histories and training records.
Most of the cost is evidence, not filing
The filing charges are published and should be taken from the current schedule rather than from an earlier case, since L petitions can attract more than one charge and some depend on the employer's workforce. Around them, an L-1B file has a characteristic cost profile. Corporate counsel has to read the joint venture agreement and give an opinion on control, which is unavoidable when the relationship is not a simple subsidiary. Quality and operations staff have to extract documents from a controlled system, redact what is commercially sensitive and prepare exhibits. Somebody has to write a duty description that is technical enough to be credible and clear enough to be read by a non-specialist. If a request for evidence follows, the same people repeat the exercise under time pressure. Companies that treat the first file as the cheap version usually pay for both. Set the budget for one thorough submission.
Hypothetical example: a specialty-adhesives manufacturer plans to transfer the chemist who designed its proprietary curing sequence. An initial review should yield a document list with owners, redaction rules, and dates: the joint-venture agreement for control, protocol revisions for company-specific knowledge, training records for scarcity, and payroll history for the qualifying employment period. The business must decide whether it can disclose enough of the process to make the claim testable without surrendering trade secrets. What goes wrong is a budget that pays for filing but not for technical review, translation where needed, exhibit preparation, or a consistent explanation from the people who own the records. Sequence the work by securing the corporate opinion first, then preserving technical records, then drafting duties from those records. That prevents an impressive narrative from being contradicted by the source documents.