Even if the firehose was affordable for mere mortals, those mere mortals would still need the funds to receive potentially hundreds of thousands of tweets per s

Even if the firehose was affordable for mere mortals, those mere mortals would still need the funds to receive potentially hundreds of thousands of tweets per second (peak)) – which is a lot of bandwidth, persistent storage, processing cycles, etc – and that doesn't come cheap either. If someone can't afford access to the firehose, then my guess is that they can't afford the infrastructure to consume the data anyway.