There are 67 authors on the PaLM paper. Assuming average salary of $150k (probably a large underestimate for Google employees) that's $10M+/year in salary alone. Compute is a big cost factor for this project but it's not clear if it even dominates the total cost.
In the long run this type of research will more than pay itself back in benefits to Google. NLP underpins everything they do. It would be interesting to see how OpenAI API (GPT-3) is doing in terms of revenue. They're going for the more direct method of seeking value from a trained large language model.