There's a book entitled Multicultural Manners that addresses cases like this.
In the book, there was an example of a boss who asked his employee to make some treats from her culture, for him to serve guests. She makes the items, and when he picks them up, he offers her money for her work. In her culture, the 'three times' rule applies, so she says, no, no, it was her pleasure. The boss pulls out his wallet and says, no, let me pay you something, at least the cost of the ingredients. The employee again reassures him that she didn't want anything, it was her pleasure. The boss thanks her again, and walks off with the treats. The employee waits for him to leave, then bursts into tears, because she was expecting him to offer again, and then she could say something like, 'The ingredients were $30, and it took me 4 hours to make,' at which point she expected him to hand over $30 plus what he though 4 hours of her labor would be worth.