Show Me the Numbers: Serial's Data Transfer Costs

Serial is the most accessed podcast ever from iTunes, according to Apple. By November 18, it was downloaded and streamed 5 million times. The show claims some 1.5 million listeners per episode, of which nine have so far been produced. That would mean nearly 9 million downloads or streaming sessions (assuming people went back to listen to the whole thing) from non-iTunes sources, which seems high, but would also indicate a better distribution of means by which people obtain podcasts, which is good for all podcasters!

David Carr, the lead media reporter at the New York Times, wrote that the episodes were downloaded "at a cost of nothing," which may refer to what it costs to deliver or what listeners pay; hard to tell. But I'd like to guess at the amount. What does it cost to deliver that many episodes?

Let's take the notion for simplicity that roughly 13.5 million downloads or equivalent streams occurred evenly over three months, or 4.5 million downloads a month. Episode 9 is typical and roughly 30 megabytes (MB). That's 135 terabytes (TB) per month. (Yes, some months would be more and others less, but still good for estimating.)

Via Amazon S3, Serial would have paid $12,000 a month or $36,000 so far. Amazon charges on usage, not on a monthly basis. (It charges for storage on a monthly basis, but all the podcast files together aren't even half a gigabyte.)

But, as my information technology friends tell me, that's way too much to pay; instead, Serial is using a content distribution network (CDN), which is designed to take media files and feed them out a bazillion times more cheaply and efficiently. Serial's CDN, Highwinds, doesn't publish its rates and any CDNs only offer private estimates, but MaxCDN has a rate schedule. Serial would pick the 150 TB per month plan, which runs $6,144 per month plus 4¢ a GB over 150 TB ($40 per extra TB). That would be over $18,000 so far. CacheFly has a bandwidth calculator, and reckons a bit over $3,700 per month for 135 TB, or about $11,000 so far.

If Serial has cut an excellent deal, piggybacking as one expects on This American Life's downloads, it's probably paying the least possible, and that sub-$4,000 per month figure seems accurate. But in public radio, that's the same cost as part or all of a full-time entry-level-or-above position. If the show becomes more popular, the costs go up as well, where conventional radio distribution has a very high fixed cost and none of these sorts of high variable costs for extremely popular programs. Some podcast and audio hosting sites, like Libsyn and SoundCloud, absorb some or all of the bandwidth costs — but they're still paying the piper, even if they bill $0 to the podcast producers.

Over time, the price of data transfer has dropped relatively quickly, but it doesn't plummet nearly as fast as hard drives or hosted storage. In 2006, Amazon charged 16¢ per GB for downstream transfer (its servers to the Internet); in 2014, it's 33% lower, or 12¢ per GB. In the same time, hard drive storage dropped from 60¢ per GB to 3¢, or a 95% drop.

Increasingly successful podcasts will need to budget serious sums that, as listenership grows and prices slowly drop, might stay constant for a while, and be a significant line item in the budget.