Think its quite common, im an agressive undercutter on the AH esp at the start of an expansion.
Ill often farm up tons of ores/herbs etc and when i list them get some whispers about my prices. I just reply saying you dont like the prices, buy em up and relist
Its always a good way to shift lots of stuff quickly.
Gold isnt valuable in wow anymore since its all vanity stuff to buy with it and without doing cutting edge raiding theres no way im using BMAH or buying raid gear etc. So i have fun undercutting.
Most of the guys who dominated AH economies were the ones freaking out when connected realms were emerging as they had cornered their own market for ages.
I always use sites like Undermine Journal to get an idea of whats selling well on realms and then go undercut
passes some time in a pre expansion lull