Difficult client on cabinet repaint job in Idaho - won't pay the $850 balance after I fixed their mess

Up in Idaho, just wrapped a kitchen cabinet repaint with Sherwin-Williams Emerald urethane, quoted $850 total for the whole job including prep and two coats. Client nitpicks every little thing, had me redo doors twice, now refuses to pay the final 40% saying it's not 'perfect' even though I matched the color exactly. Saw this Idaho Painter video on Twitter demoing HVLP spraying for cabinets, thought it was spot on but these clients still find issues. FML, chasing this check is killing me.