Many of these techniques haven't been published very long ago - it often takes a good 6-8 months for techniques to percolate. But also, they come at a complexity cost and, seemingly, also at a stability cost.
Also potentially a performance (in terms of output quality) cost. DeepSeek is cheap on a per token basis but lags behind in the benchmarks, perhaps it was a calculated tradeoff.
It very much possible Anthropic, OpenAI and Google able to serve their models much cheaper than their current API prices.
They just dont do it because they dont try to ubdercut each other and so far chinese models been percieved behind SOTA.