Open source models apply pressures on the low end of the market. The paid models are so much better that they can charge based on value for enterprises.

I wouldn't call Kimi K2.6, GLM5.1, DS4 or newer Qwen models "low end". I prefer GPT5.5, but if it disappeared tomorrow, I'd be perfectly fine with any of these chinese models.

Have you used any of the recent models? My experience with GLM 5.1 does not make me miss Opus at all.