Apple recently provided a sneak preview of its latest retail store in San Francisco’s Union Square ahead of its grand opening, and building permits shared with BuildZoom (via Patently Apple) have now revealed some of the costs involved in buying and prepping the store.

The signature glass staircase is always one of the most expensive elements in an Apple Store, this one coming in at a cool $1M – or $33,333 per stair. But surprisingly, a rather more mundane item cost more: an upgrade to the building’s sprinkler system came it at $2.28M. The fire alarms were clearly in better shape, as the upgrade cost there was just $4,000.

No cost was shown for the headline feature of the store: the full-height doors that allow it to open to the street on both floors.