I agree, it's not all about the ticket prices or other cost in purchasing merch, it's all about people and the supporters are losing interest with them because of repetitive teams playing in the semis, supporters know how the team plays and they can easily predict who will become the winning team, But I don't know if there's still a lot of people still watching them once it was aired on television.
There are still some but most of them are those who are betting on the games. Actually, they can reach many viewers online like their facebook stream depending on the teams that are playing, if it's Ginebra then that's guaranteed they'll get a good number of viewers. However, there's a problem with their streaming as it's not really a live telecast but more likely a delayed telecast, that's why people would just choose to watch from the illegal streamers as they provide what people are looking for. Just imagine you are betting on a certain game but what you are watching was a delayed telecast, how can you win?