I just spent the last 9 or so hours on Purevolume, more or less just continuously playing music. For those unfamiliar with the site, Purevolume is a place where bands can upload mp3s, which listeners can access and stream.
These mp3s must be like, 4MB each. How much does each play cost Purevolume in bandwidth? I can’t imagine it would be cheap, but I really have no idea.
In the purest sense each MP3 downloaded adds nothing to the bandwidth cost. They’re probably paying $x,xxx dollars a month for their Internet connection(s) whether it runs at 0% capacity or 100% capacity.
If you wanted to try and put some sort of rough price on each MP3 served, you’d have to divide the cost of their Internet connection by the number of MP3s they served. Of course we don’t know those numbers.
That’s true at low levels, but for higher bandwidth connections, the charge is typically per amount of data. Even if they were paying a set fee, they would carefully tailor that set fee to meet their bandwidth needs and no more, so each additional download would have an effect. Enough of them, and you have to go up to the next tier.
I don’t know the answer to the OP’s question, but here are some back of the envelope calculations to give an idea.
A T-1 line (that a small business might have) runs at 1.5 Mb/s, and costs ~$500/mo. Using it at full capacity, that’s around 250 GB transfer per month, or $2/GB.
A T-3 line runs at 45 Mb/s and costs ~$10,000/mo. Using it at full capacity, that’s around 10 TB transfer per month, or $1/GB.
mp3s are usually about 1 MB/min, so if you were playing music for 9 hours, that’s about 500 MB. The bandwidth for that probably cost them on the order of $1.