This is not generally true. Inference costs have just began to spike starting with the 'test-time scaling' trend[1]. I imagine most OpenAI users are free and the mini models available to them only cost a few cents per task[2]. The chart from The Information featured in this Reddit thread seems more reasonable[3].
Although that was posted in October, so not much time for the reasoning model costs to show up. It's also important to note their revenue is on track to more than double this year[4] and one can't make a complete picture without understanding the revenue spent on the inference provided by these reasoning models.