I use mollies for my feeders. they breed pretty quick for me.
Also I do not think that raising feeders is expensive. I have 4 tanks, 1 is a community tank, 1 feeder tank, and 2 predatory tanks. The feeder tank eat the same food as my community and there is no real cost to raise the fish. For me is it like another tank in the house. If I did not have feeders in there, some other fish would be there. But that is just my 2 cents
Also I do not think that raising feeders is expensive. I have 4 tanks, 1 is a community tank, 1 feeder tank, and 2 predatory tanks. The feeder tank eat the same food as my community and there is no real cost to raise the fish. For me is it like another tank in the house. If I did not have feeders in there, some other fish would be there. But that is just my 2 cents