It really depends on caching[1] and active parameters, and some dark arts really only possible at Hyperscalers they also have better access to 288GB VRAM B300s[2] that really makes a difference in cache space.
K3 may be bit smaller/ similar in total parameter count than Opus, but Opus (and GPT) definitely has become a lot more efficient in the last 6 months or so, hence more or less forced upgrades. I expect the active parameter count and cache performance is quite different.
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Opus is still almost twice as expensive (if tokens were equal) at $5/$15 compared to K3 at $3/$15. Tokens are not equal though, Anthropic's tokenizer is much less dense than other frontier lab's so the actual price difference is like 3x.
Kimi uses more reasoning tokens and is generally more inefficient with its usage, that doesn't impact token cost economics for the provider though . It does for us as buyers thus the need to evaluating by Cost per task rather than unit pricing.
On pure tokens/$ - there is definitely room for a price war if operators start going by pure unit costs. Both probably want(ed) to have good enough numbers in preparing for the IPO.
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[1] the pricing kind of reflect this already - 10x diff for uncached input.
[2] Moonshot does not have access latest gen GPUs so their unit economics is likely hampered a bit for high parameter models.