It's been said to me that compared to actually making a film, writing the script is free. I used to buy into that...
But unless you're getting paid for that writing then it is actually not free - it costs time to write and that is time you could spend earning a wage, supporting your family, getting out of debt, etc. Y'know, real life adult shit.
I made this simple little table to keep me grounded on just what it will cost me to take time off from 1st/2nd A.D.'ing to complete a feature script.
First put in your expected script length, followed by how many pages you can crank out in a day on average (be honest with yourself!). The result will be how many days (gross) you'll need, rounded up, at that page rate in order to complete the script.
The next part brings in some reality and takes your basic work week info (e.g. I often work 4 day weeks), reveals how many free days you get, at your given wage, and how much that time off will cost you.
I had a line inserted adjusting for family time but that just clouded things. Keep It Simple, Idiot. No, wait...