Airut bones are the remains of airut, obtained when an airut is killed. Airut bones give 132.5 Prayer experience when buried. This is increased to 463.7 experience when using a gilded altar with lit burners, increasing to 491.5 experience when combined with a clan avatar or 530 experience when using the ectofuntus.
A player choosing to use airut bones all the way from 1-99 Prayer, using a gilded altar with lit burners and no other experience boosts, would, if all the bones were bought at the current medium price on the Grand Exchange, spend 167,449,008.99.
Additionally the first bone used would take them straight to level 5 Prayer.
Using the ectofuntus would cost 146,502,085.79, but would take far longer to do. Simply burying the bones would cost 586,008,343.15.
After an update, airut bones were physically increased in size, to better match the creature they came from. Prior to the update, the bones were similar to the size of regular bones. This update made the bones appear to occupy a 3x3 space.