The main ones are professional review of the arrangement, the employer's cost of preparing a proper letter, and travel. Government charges depend on the route used and should be taken from the current USCIS fee schedule rather than from a figure quoted informally.
Weigh the preparation against the length of the engagement
A short seasonal engagement carries much the same preparation as a long one, which changes the arithmetic. It is worth asking the employer early whether the role is genuinely a season or the beginning of something longer, because that answer affects whether the effort makes sense for either side. Ask an adviser to price the assessment separately from any filing, so that a decision not to proceed is not an expensive one.
Where the employer expects the individual to carry all costs for a role of a few months, that is a reasonable thing to negotiate rather than to accept, and it also tends to reveal how committed the employer really is. Hypothetical example: Sora is offered an eight-month assignment validating air-quality sensors for a municipal-equipment maker. A cost review should separate unavoidable government charges from translation, credential, travel and employer-document costs, then compare them with the likely length of the engagement.
The offer letter is the record that settles whether the job has a defined temporary period and who bears particular expenses. Ask for that clarification before purchasing travel or commissioning specialist reports. A frequent mistake is ordering an expensive credential opinion before confirming that the support relationship and employment structure fit the category; credentials cannot repair a role that is framed incorrectly.