gpt5 has always been about making a "collection of models" work together and not about model++. This was announced what, a year ago? And they delivered. Capabilities ~90-110% of their top tier old models at 4-6x lower price. That's insane!
gpt5-mini is insane for its price, in agentic coding. I've had great sessions with it, at 0.x$ / session. It can do things that claude 3.5/3.7 couldn't do ~6 months ago, at 10-15x the price. Whatever RL they did is working wonders.