(You don’t collect your own BP or medal awards, of course.) Since the level 80 arc reward is substantial, this may make levelling your GB exceptionally cheap. In effect, a 1.9 thread is like self funding your GB except that you collect the FP rewards yourself and you collect them as if you have a level 80 arc, rather than at your own arc level. They can also very quickly level their Great Buildings in ways they might not otherwise.

While people may not make much FP profit, they can get a lot of additional Blue Prints and medals. This way, participants get a return on their Forge Points sooner, and they are not locked up for days. Most 1.9 Guild Threads stipulate a person must level their Great Building within 48 hours of it being posted to the thread. Only if they have an 81+ Arc is there generally an opportunity for a small profit. In most cases, guildies do this without making a profit. Other members on the thread than donate to lock the first through fourth spots. People post the Great Building they want leveled to the thread.

People with lower level arcs may be allowed to participate, but they will suffer a loss when they take a spot offered in the thread. 1.9 Guild Threads are for people with Level 80+ Arcs only.

Arc forge of empires wiki