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When Baldur's Gate 3 came out, Steam's overall bandwidth consumption went from around 18 Tbps to 146 Tbps
(reddthat.com)
From Steam's self-published stats.
Baldur's Gate 3 could not be preloaded and weighed in at 125 gigabytes on disk, so when the game left Early Access at 11am US Eastern yesterday, Steam's bandwidth utilization shot up 8x over a span of 30 minutes. I know personally, I saw my download hit over 600 Mbps across a 1 Gbps fiber connection.
Kudos to the system engineers at Valve. It is mind-boggling that they have built infrastructure that robust.
You're not going to see it unfortunately. They'll just assume that you're on gigabit and will spend 3 hours downloading it.
In a Datacenter that I have some equipment in, it's $300 a month for 1gbps. At that cost, 3 hours of bandwidth costs them $1.20... this is cheaper than any current device that can hold 1TB by leaps and bounds. Forget that they'd have way bigger pipes than that and at a much better cost/gbps.
On top of that you can also program stuff to do distributed file serving (eg. bittorrent) to alleviate the datacenter costs too. So that $1.20 is a "worst case" scenario... and the costs plummet hard at each cost-cutting step they could take.