I'll take a stab at it. Please correct me as you see fit.
.5 acre lawn is 21780 sqft
You would need 152 gallons of tea for application
152 gallons of application tea in a diluted (3:1) state is 50 gallons undiluted.
I havent seen actually number on what you need to brew, generally just a few shovels into a bag to brew. So lets call that a cubic foot?
So a cubic foot of compost (plus tea growth supplements) is enough for a half acre application?
Honestly seems like the water bill will be the biggest cost after production is running.