I couldn't find value for money with CE, though I've found a hack with unlimited harvester resources:
Empty harvester has cargo value 0.0 (float), fully loaded harvester has cargo value 10.0. Search for this float value and freeze it to 10.0 - then harvester will be unloading endlessly providing you unlimited income.
P.S. for high expense rate you'd need to build 2nd gas factory and hack another harvester.
P.P.S. You can sometimes hack enemy harvesters and freeze them to 0.0, effectively slowering enemy's income.