GGB No honest article can hand you that figure, because it is the product of your own manpower plan: which roles, in which waves, landing how early, at what loaded cost — salary plus recruitment, authorisation and medical costs as a category, relocation, housing and training time. The method is to price every hire from acceptance through opening night inside the feasibility model, as its own budget line separate from post-opening salaries. The common failure is not mis-estimating the line; it is omitting it, and discovering it mid-build inside the working capital.
From The Pre-Opening Recruitment Calendar — Hiring Backwards from Opening Night — the full reading, with the method behind this answer.