Anthropic is getting capacity from Colossus 1 not Colossus 2 it sounded like. The initial colossus capex was under $5B, making that an even more astounding payoff.
Edit: S1 states both are being leased so the 20-25B initial investment probably more relevant
The S-1 states that it gets capacity from both Colossus 1 and Colossus 2.
... and a sign Anthropic couldn't find enough compute anywhere else, so they had to bite the bullet. Interesting.