Are we in an AI Bubble? Lessons from 1873 and 2000

The author compares today's AI buildout to the 1873 railroad boom and the 2000 dotcom bubble, noting that AI infrastructure spending is roughly three times larger than the dotcom buildout and double the 19th-century railroads. He argues AI companies have much larger operating cash flows than dotcom-era firms, but worries about who will ultimately pay for AI, citing concentrated spending, slowing growth among the largest customers, and a 41% decline in effective price per million tokens between March and August. He concludes he does not think we are in a mania bubble but is unsure the enormous AI investments will pay off.