Say you buy good coffee at \$120/kg, calibrate it carefully, serve a 20g dose, and charge \$8 for it. Your gross profit* per sale is \$5.60.
Say you buy bad coffee at \$45/kg, serve a 20g dose, calibrate it roughly, and charge \$7 for it. Your gross profit* per sale is \$6.10.
* Before wastage.
Ignoring the difference in machinery completely... you make \$0.50 on cost of goods, save time and energy, and save \$1.00 for a customer who doesn't care. This is a win-win scenario... it only requires that you care to do it.
Nevertheless, doing so might offend certain sensibilities, and you could argue that the promotion of cheap coffee hurts the lives of people elsewhere.