I usually spend about 3-4 hours on these in total.
Also, imagine that in headshot form (I don't have any examples ;w; ) and what do you think THAT would be worth?
Considering the time spent, I agree with Juliettee's quote for waist-up, but for a bust I'd say more around 500k as a base.
If you did a fullbody, double the price of a waist up.