To find the unit price for one Paper Mate Flair Pen when 24 pens cost $18.60, you divide the total cost by the number of pens.
\[ \text{Unit Price} = \frac{\text{Total Cost}}{\text{Number of Pens}} = \frac{18.60}{24} \]
Calculating that:
\[ \text{Unit Price} = 0.775 \]
Rounding to two decimal places gives $0.78.
So, the unit price for one Paper Mate Flair Pen is $0.78.