Human beings contain mana, which is the energy required for life. Mana grows over the course of a person's life, being released at the moment of death. Demons can feed on this energy to increase their power through the creation of pacts with humans in exchange for magical power. When a demon makes a pact with a witch, the human is rewarded with a boon that allows them access to spells. In exchange, her soul goes to the demon after death. The number of souls a demon can collect, the more it can increase its own power.
This competition between demons for human souls culminated into many wars and much bloodshed among witches, which led to the detriment of everyone. To end the wars in the human world, demons agreed to a treaty amongst themselves. Instead of warring with each other for a piece of each others pie, they would share the spoils. Witches would be divided up into families called covens, each with their own patron demon. When a witch came of age or joined the family, they would sign a pact with that coven's specific demon. She would gain access to magic in exchange for her soul. Each pact is an investment for the demon, which places a seed of their power into the individual. As their Mana increases with age, the seed grows in tandem. When the witch dies and their soul is claimed by the demon, the seed has multiplied in strength, returning on the demon's investment tenfold. Through this method, a demon would be guaranteed a steady stream of souls as the coven expanded either through birth or recruitment.
This business model soon produced flaws however. It didn't take long for demons to realize that increasing the number of witches in their family as fast as possible was in their best interest. This led to a massive increase in recruitment, as many individuals among the population would simply be inducted into these covens. Potential witches were eager to sign away their souls in exchange for power from a patron, and demons were just as eager to collect more souls than their rivals. This led to a race to the bottom, as covens lowered their standards to try to outdo other covens, creating a generation of crappy witches.
What I want is for demons to value producing witches of high quality and skill, rather than turning covens into basically recruiting centers. However, it is natural for standards to be sacrificed in the name of producing content if the latter is in one's best interest. This is similiar to the streaming wars, in which most of Netflix's movies and series are crap, but it is made in such high quantities that they outpace the competition. How can I make this happen?