The main added cost is legal review time to read the option and governing documents and assess control. There may also be tax or corporate advice on exercising, which is separate from immigration advice. Government filing costs depend on the route and should be confirmed directly.
Budget for review before the vesting deadline
A control review is usually a discrete piece of work: read the grant, the plan, the share register, and the shareholders' agreement, then advise. Doing it before a vesting deadline is less work than unwinding an exercised position later or rebuilding a case that was described inaccurately. Tax treatment of an exercise is a separate professional question, and answers there do not resolve the immigration analysis.
An exercise price is a corporate cost; a control review is an immigration one, and treating them as the same line item produces a budget that omits the second. What the applicant pays to acquire shares is fixed by the grant and belongs to tax and corporate advisers. What the file needs is a reading of the instruments that decide authority, and the size of that work follows the number of instruments rather than the value of the equity: one grant under a standard plan is short, while several grants, a shareholders’ agreement and a side letter take longer.
Government charges vary with the route chosen and should be confirmed from the official source at the time of filing.