Re: The business of flies
Home fly culture is certainly the most economical generally speaking and many people do it dependably and cheaply.
I, however, am happy to pay for the convenience of someone else doing the culturing: I get 4 cultures (2 new, 2 producing) from Josh's Frogs delivered every 5-6 weeks (enough to feed my 15+ thumbnails for that duration). It costs ~$45 per order so less than $10 per week. I don't have to worry about mites or genetic decline and the only cleaning I do is to spray the plastic bin I keep the fruit flies in with rubbing alcohol between one batch and the next.
If culturing is your main pain point and $10 a week doesn't break the budget you might want to give retail flies a shot.