RMT = real money trading.
Selling an item in game for in-game currency is certainly NOT RMT, it is in-game trading with in-game currency. Buying an item from the cash shop is NOT RMT. Buying the item from the cash shop and selling it for gil is loss making by individual players, who have managed to convert good RL money into gil while donating to SE. What it does is distort the distribution of gil for a short time, because the percentage of players with excess gil that can afford to part with that gil is very limited like the top 1% or so. For it to be affordable for large numbers of players the, converting $10-40 for nominal amount of gil like 500K is just ridiculous. This mad rush for converting wedding bands into gil is self-limiting and unsustainable.
There is no profit when it is all in gil. The profit can only occur when you sell the gil to get real money and produce real profits. People trading on the MB can make gil gains all the time, you can even call that MB trade profitable. And getting gil in-game is far cry from pay-to-win, even if you can afford 110 crafted gear, the poetic gear and FCoB drops are at 120 and above.