I think you should examine your statements carefully.
Airbnb. The nature of renting a room as a hotel is such that you can’t do it without a marketplace as the cost of acquisition would be impossibly high.
Ticket Master monopolises it’s supply with long term exclusive contracts. If you want to sell tickets to a gig at the O2, you literally have no other choice. Their business mode would fail without the exclusivity. Imagine 20 companies all selling O2 tickets and willing to reduce the “ticket charge” to win the client.
The point is this. If you can’t lock in your most successful suppliers, they will leave and compete with you for the same customers and destroy your margin.