Let me make some changes to your list
Old computer (garbage day, garage sale)Old joystick or gamepad (garbage, garage sale, basement, cheep co. store)
17" Monitor (basement, garbage, garage sale)
Extra storage (garbage, basement, newegg)
Button set (~$30 online)
Linux (free - internet)
Mame (free -internet)
Arcade cabinet: ~$25-100
I saved you $300, have fun