I wasn’t calculating server costs, just raw storage. Google is not buying hard drives at retail prices. I wouldn’t be surprised if they’re paying as little as 50% of the retail price to buy at volume.

All of what you say is true but the purpose was to get a back of the envelope estimation to show that the cost of storage is not a truly limiting factor for a company like youtube. My point was to answer the question.

With the level of compression youtube uses, the storage costs of everything below 4k is substantially lower than 4k by itself: for back of envelope purposes we can just ignore those resolutions.