> My consumer line is measured in megabits per second and if I have to pay for my data usage the way it's paid for in data centers it would be far more expensive

Well because your provider assumes you are not using all your bandwidth constantly. Cloud bandwidth is only billed for you actually use

It's still true that "clouds" cost much more than proper internet connections at DCs. E.g. AWS wants you to pay $90/TB, Hetzner $1.50/TB, a good deal on a contract is probably half what Hetzner pays since they need profit too.

And if you have two specific endpoints you need to transfer data between at a high rate, you can get stupidly cheap cost per GB on a leased line in exchange for making all that commitment upfront.