General Method Description

Mahogany logs are primarily used to make planks for the Construction skill. They have traditionally not been very valuable, and the need to travel to Tai Bwo Wannai and pay for access to the grove where they are located led them to become quite unpopular. But in late 2009, Jagex made some updates to the Woodcutting skill, and one of these made mahogany logs more attractive. About every 70 or so logs, you get a "special" mahogany log with a striped pattern on it. These untradeable logs are of value to the sawmill operator; he will pay 3,900 cash for them, or even better, if you bring him two of these and an inventory of regular mahogany logs, he'll plank all the regular ones for free! This makes the effective value of each of these logs a whopping 19,500 gp (two special logs lets you save 1,500 gp on each of 26 regular mahogany logs.)

If you plan to cut mahoganies extensively, I recommend relocating your house to Brimhaven and setting your arrival point to the portal. An alternative is to use fairy ring code "C K R" and then run northeast, but this means you lose an inventory slot.

Use a beast of burden here to cut down on travel time. A spirit terrorbird is fine until you can use a pack yak; war tortoises are too expensive to justify their cost.

Note that the methods here do not take into account the time required to make logs into planks. The most efficient way to do this is to start at Castle Wars and summon a spirit terrorbird. Take out of the bank one set of willow logs, two special mahogany logs and 25 regular mahogany logs. Put one mahogany log set in the terrorbird and take out another. Run over to the hot air balloon and travel to Varrock. Take the extra logs from the terrorbird, talk to the saw mill operator and tell him to plank your logs. Teleport to Castle Wars and repeat.

Note that birds' nests are not included as output here as they are too rare and unpredictable for me to estimate their average value.