I imagine it's a mix of: 1. text-davinci-003 is subjectively (well, and objectively) better than other models 2. for small-ish usage volume, Davinci and Curie

I imagine it's a mix of: 1. text-davinci-003 is subjectively (well, and objectively) better than other models 2. for small-ish usage volume, Davinci and Curie are both pretty cheap in absolute terms that a 10x factor doesn't matter 3. GPT3 hype