Government charges are published in the USCIS fee schedule, Form G-1055, with optional premium processing. The substantial costs are internal: producing and organizing the proprietary documentation that proves specialized knowledge, reviewing the customer contract, and counsel's time responding to a request for evidence, which this classification attracts more often than others.
The expensive part is proving what the company knows
Specialized-knowledge petitions are evidence-hungry, and much of the evidence has to be created rather than collected. Method documents may exist only as working files, training may have been delivered informally, and the knowledge that everyone in the company takes for granted may never have been written down. Preparing that material properly occupies engineering time as well as legal time, and it is the reason a first petition of this kind costs more than the employer expects and a second one costs less.
Where the assignment is at a customer's site, the service agreement may need amendment before it can support the petition, which involves commercial negotiation and its own legal cost. Government fees are the predictable component and should be read from the current schedule. Premium processing shortens the wait without improving the file.