I worked with the enterprise sales team for awhile when I worked at Udacity and we did some research on job motivations to help answer questions about recruiting & retaining good engineers. We found that salary needs to be “enough” (varies by local market) but that people will literally relocate their families and lives to work on problems that they find interesting and that are a unique opportunity. The salary bump needs to be very large to achieve the same effect as “amazing opportunity”.

Both may be benefiting openAI here. There’s lots of places to work on LLMs but “GPT” is a product/brand that people have heard of, and if OP is to be believed then they certainly seem to be paying “enough”.