There is nothing suspicious or abnormal about this behavior. It is called competition. Ironically, trying to prevent this kind of behavior prevents competitiob, and is a key factor for causing monopolization
It depends... if OpenAI bought the DRAM in order to use it, then fair play to them.
If they bought the DRAM in order to stop their competitors from using it because they are falling behind, that's anticompetitive in spirit, though I'm not sure if it actually breaks any laws.
Knowingly attempting to buy or sell in quantities likely to move markets, for direct profit, is called manipulation and is most definitely illegal. this is true in physical markets commodity markets and financial markets. Not saying that this is what openAI is doing but it definitely merits an investigation.