It takes a lot of searching to gather the information, but having done it for the airports that are options for me, I reiterate:

1. If there are options from multiple airlines for your destination from one point of origin, all options from that point of origin tend to be cheaper, because everyone changes the price to keep pace with the cheapest option.

2. There appears to be a premium charged for direct flights.

Do these not fit with what you are seeing?