This is Microsoft subsidizing Claude inference costs -- if you look at how they charge models against your allotment, Gemini, GPT-5 and Claude 4 Sonnet all cost the same, despite Claude 4 Sonnet being more expensive than the other two. Not really sure I understand the economics here, especially since there's not really a clear winner between GPT-5 and Claude 4 Sonnet for coding (if anything I think GPT-5 puts up a better showing).