The petitioning employer files and pays. Costs include the USCIS fee for Form I-129 with the L supplement, any fraud prevention and detection fee that applies, and premium processing if requested. Current amounts appear in the USCIS fee schedule, Form G-1055.
A delayed project spends the budget twice
The initial filing is the smaller expense. What raises the cost in a case like Solomon's is the documentation of the process itself, because the company has to write down something it has only ever run, and that takes engineering time rather than legal time. Where a request for evidence arrives, the response usually needs the same people again.
If commissioning slips and an extension becomes necessary, filing fees and professional fees recur, and the company also carries the cost of a senior tradesperson being unavailable in Bonfield for longer than planned. Confirm figures on Form G-1055 rather than reusing an old quote, and agree in writing whether the employer covers dependants' costs, which are frequently overlooked until the family is already committed.