Important to note: the $5 million alleged cost is just the cpu compute cost for the final version of the model; it's not the cumulative cost of the research to date.
The analogous costs would be what OpenAI spent to go from GPT 4 to GPT 4o (i.e., to develop the reasoning model from the most up-to-date LLM model). $5 million is still less than what OpenAI spent but it's not a magnitude lower. (OpenAI spent up to $100 million on GPT4 but a fraction of that to get GPT 4o. Will update comment if I can find numbers for 4o before edit window closes)
It doesn't make sense to compare individual models. A better way is to look at total compute consumed, normalized by the output. In the end what counts is the cost of providing tokens.
The analogous costs would be what OpenAI spent to go from GPT 4 to GPT 4o (i.e., to develop the reasoning model from the most up-to-date LLM model). $5 million is still less than what OpenAI spent but it's not a magnitude lower. (OpenAI spent up to $100 million on GPT4 but a fraction of that to get GPT 4o. Will update comment if I can find numbers for 4o before edit window closes)