Here is another must watch video on this vexed issue of working for free / mates-rates / working at a loss. This one is from mixing legend Tony Maserati and applies equally to screen composers. It's a perfect compliment to our earlier post this year from composer Jason Graves (https://www.agsc.org.au/news/never-work-for-free).
TL;DR? ALWAYS place a value (monetary or otherwise) on what you do.