You are dealing with two separate feedback mechanisms. One allows the creation of revenue via consumer purchases. That is the quantity companies hope to increas

You are dealing with two separate feedback mechanisms. One allows the creation of revenue via consumer purchases. That is the quantity companies hope to increase, and limiting a consumer to authorized components allows for higher margins by artificially limiting competition and increasing the revenue. Albeit inflationary, that works until a competitor figures out an effective forging method. The other is brand reputation, whereby future purchases are dependent on how a consumer feels about the brand. You state that such tactics cannot look good for the brand, but remember that there is a delay between the large bulk of appliance purchases and the time when consumers would be writing bad reviews, affecting future purchases. By the time this cause and effect chain concludes, most of the benefit for the first feedback mechanism has already realized, and the vendors can move on to the next deal. Keep in mind that consumers do not necessarily look at filter compatibility when making a purchase, and companies can capitalize on that. Both mechanisms contribute to stock value, but your surprise might stem from the fact that their contribution is uneven. In other words, short term monetary gains trump long term brand gains, because consumers have short memories.