Spain had helpfully disarmed lowland and vulnerable communities throughout out the islands so few had the ability to defend themselves. As late as 1864 many communities had little more than sticks and rocks in their armouries.
The only effective strategy against the slavers would have been for the Spanish to combine forces with the British and the Dutch, each of whom mutually hated the other as empires are wont to do. Think ABS-CBN and GMA or San Miguel and Asia Brewery. Or somebody big and somebody else equally big.
The economic effect was devastating. Samar’s tiny population lost some 500 people a year. Nueva Caceres alone lost up to 1,500 people a year. Even Manila Bay came in for trouble. Regular destruction of the coastal communities made the growing of crops, especially cash-crops a futile gesture. But the Iranun and Balangigi did quite well out of it, capturing around 300,000 slaves during the great days of slave-raiding, a fair chunk of the tiny Filipino population of the time.
Being an employer in those days in the Sulu Archipelago had a certain simplicity, or did it? After all, this was Filipino slavery. One wouldn’t expect Filipino slavery to be quite the same as anyone else’s and it wasn’t, as we’ll see.