Most people are legitimate and won't charge as they enjoy it but you have to remember projects whether it is builds or modding, they take a LOT of time and effort and people don't just hand out their time freely, they have other things to do as well.
So you have to appreciate that yes, I should pay them as they are giving u[ their time for me.
But the guy you are talking about is just a complete scam artist, and a nub at that..