Aryn Drake-Lee filed docs claiming the $50,695 per month Jesse's been ordered to fork over in spousal support falls way short of covering expenses for their kids, ages 4 and 2.

In the docs, Aryn says she's paying 100% of the kids' bills right now ... including clothes, food, traveling outside L.A. to visit family, swimming and dance lessons, child care and tuition. Aryn says that pushes expenses to $73,369 per month.

Aryn claims Jesse can afford it since he makes at least $250k per "Grey's Anatomy" episode, so she wants to be reimbursed for what she's had to cover so far.

On top of that ... Aryn wants $200k to cover her legal fees. We broke the story, Jesse agreed to front her $60k for her lawyer's fees ... but clearly that ain't cutting it for Aryn.