While I don't necessarily agree that it would run dry, I do see where you are coming from. Why would Epona run dry on gold tho? If people are buying up it's gear, then it would have a crap load of gold. I would imagine that price would become too high for out of server people to find it worth while to buy gear rather than obtain it from it's clan (if they aren't already doing that).The biggest issue with the cross server auction house is that it will never really work for gear if other servers continue to refuse to sell drops. Epona will be sucked dry and the flow of gold will slow down for the server. I personally think it would be best if other servers allowed the selling of drops (if global auction was made) because it would benefit the game economy as a whole. As of right now gold has hardly any buying power like it should have on many servers because there’s simply not enough things to buy, which causes inflation. It’s why you see things on Epona being sold for dirt cheap when compared with other servers. When gold has more buying power people are tempted to buy more and more chests, which makes plat items cheaper which makes everyone better off.
To combat too much flow of gear from one place, vr could implemnt a taxing system. For items less 100k, out of server buyer pays a 20 percent tax, less than 1m could be 30 percent and above a mil could be 50 percent. This would allow people to buy consumes without too much penalty but buying things like gear would be made difficult.