I'm trying to think how to explain it without using anecdotes, as I want to understand it myself without punting to simile. I know that I undervalue the importance of money in my own life (I have been poor to the point of homelessness once, poor the point of selling possessions to get rent/food money a few times). I also undervalue my worth, almost never charging an appropriate amount for my time.
I've cultivated a niche expertise that I translate well to a wide range of communities, but when asked politely I tend to give my time and even tangible goods away for free.
Now, I'm actively trying to change that. I'm getting married next year and am very excited to have a family in the relatively near future, so I'm paying off debts, I re-entered the workforce at a decent salary, and have been trying to train myself to be comfortable asking people for money in exchange for my time & expertise.
It has been harder than you might imagine, but I'm making progress. Being able to externalize the need to earn money via the idea of a future family has helped me, but I remain very uncomfortable asking and often find myself under-reporting hours spent, transportation costs, etc.
If I could just produce content, conduct research, give workshops & lectures & have someone else handle the money, I would be in heaven, but the few people I've spoken to about it, despite initial enthusiasm, have never followed through. Considering my own disposition, I obviously don't blame them at all :)