Usually no additional government charge, and a great deal of everything else. The expense is a second evidence assembly under deadline, the internal hours it consumes, and the delay to a start date that the business has already planned around.
The second round is where the money goes
Requests for evidence on specialized knowledge tend to ask the question the petition avoided: what does the organization own, and what does this person know about it that colleagues do not. Answering that late is expensive because the underlying records still have to be found, and now they have to be found quickly. Costing a petition honestly at the start therefore means costing the evidence, not the forms. Check the published fee schedule for current amounts and any optional faster-adjudication charge, then set beside it a realistic estimate of the hours needed to produce contemporaneous documents, translations and a truthful account of staffing depth.
Hypothetical example: a manufacturer of dust-collection and spark-detection systems near Roxton Pond files for a commissioning technician using a general description of his skills, and receives a request for evidence eleven weeks later, three weeks before the customer’s scheduled shutdown week, which is the only window in which the equipment can be installed. The company now pays for the same work twice and for the disruption once. The cheaper path was available at the outset: two days spent locating firmware revision records, customer commissioning reports and the internal training curriculum, and one honest paragraph about how many colleagues could do the same job.