In being empathetic to their needs, make sure you're also being "empathetic" to your own needs. This means recognizing that their "need" to get their development work done without spending too much money on you is directly opposed to your need to have healthcare and money for rent, food, etc.

Obviously neither of these needs can be successfully ignored, but thinking of it this way helps me mitigate the guilt that comes with asking for more, without engaging the "winning" rhetoric even subconsciously.