I don't.
OK here is a cut and paste:
Tank 400, stand 250, MH 400, skimmer 250, custom made sump 100, eheim return 160, tunze stream 370, chiller 300, blueline closed loop pump 150, various hoses and pipes and valves and stuff 200
All this is rough, not exact. Maybe add another 200 bucks for rounding errors and stuff I've forgotten to mention. Shhh. Don't tell my wife.