Subscriptions are to keep the lights off, servers on and server maintenance and improvement. Then purchases of expansions covers the cost of development.

MTX in such a game is a bit weird, but it does give something for extra asset creation and animation. I suppose if they make something that doesn’t end up being used they can repurpide it as a pet or mount.

It’s the trading money for gold and the effects of the economy in wow that put me off.