How did you land a job without a price tag on it already?
Based on 8 hour days, 16 hours vs 24 hours is a dramatic difference.
Shop rate of $100 per hr, that would be $1600 or $2400, quite a spread.
What is the tooling cost of $300? Are these general purpose end mills/cutters or something specific (custom) for this job?
Material, mark up 15-20%.
So far it looks as though the total job would be $3180/20=$159 each part in lots of 20.
Will the customer pay this? If he agrees, go for it. Collect COD.