What is almost never considered is that these large corporations don't pay public pricing. It's all negotiated to be heavily discounted. Bandwidth is hardly an issue like it is for regular customers.
Not to mention Atlassian are moving bitbucket to be in the same cloud as their other services. They likely could have negotiated a cheaper per unit cost on their entire cloud workload, thus its possible this has generated a saving for Jira, confluence and all.