Simply by selling ur item for 1g on say danu, and buying it IMMEDIATELY for 1g on like, Mabon.
Idk how or if its possible but just like hawkhurst bots in murky, people could be bots on AH just spam buying any item that has a purchase option for say, under 10k and get any item trying to be xferred
This is a problem that has come up before on the forum. I suggested a tariff/tax for sending gold over. However, this is much different. Bots are a possibility (not impossible and its a valid point), but they are also quite easy to fix. They might have to add a "not a bot" which would actually be quite annoying.
As for the 1g, it is pretty risky to buy lux items for 1g and I am sure someone will beat you too it. It actually seems much more risky to sell in gah for 1 gold rather than to xfer through a person. Especially since you would have to refresh the page and buy while someone will probably see it and try to do the same. You would be much better off just buying it for the set price which wouldn't be abusing the gah. I can see people getting scammed by trying to do that method. YIKES. I mean I am sure it can be done, but I would never try that with an expensive rare item.
This is kind of an easy fix though I believe. Why not make it so the item must be shown on the market for 20 seconds before a buy-out can occur. I am sure many people will have their eyes looking at the cheapest buy-out price to scam people. That idea kind of promotes scammers though unfortunately. I would also suggest adding a checkbox that says "I am okay with the price being sold for this cheap to another player." for every item sold below 1k (maybe more idk).
I highly recommend not selling items lower than you want them to be sold