In the title of that article, it asks the question "What's the cost?" The answer is nothing. From the article,
They obviously know enough to keep bumping the date before they start the ad campaign.Film executives privately estimate that pushing “Mulan” or “Tenet” a few weeks at a time could amount to losing $200,000 to $400,000 in marketing fees — essentially negligible costs for a major studio in the grand scheme of unveiling a new movie. Depending on various factors, that number could increase to just under $5 million if they are delayed again without sufficient notice. That’s because the bulk of a film’s promotional and advertising efforts run in the two weeks prior to its release. So far, the release date changes have fallen outside that window.