How is that not RMT, exactly? It's buying an in-game item with real money and then selling it, presumably for gil. It's essentially buying gil for real money in the end, and I seriously doubt SE would ever go for that.

And just because other MMOs do it doesn't mean it's a good idea. It also doesn't eliminate RMT, because I know in Guild Wars 2 there's still a huge amount of spam from gold sellers. Because the two-way conversion means you can buy gold from them to convert to gems to buy gem store items. Seems a bit roundabout, but I'm sure it's cheaper in the end doing it the RMT way. If anything, it could just help RMT flourish, because people would likely be able to get Mog Station items with gil for less real money.