While monetarily the subscription is stupid expensive, several years ago blizzard added a way to pay in-game gold for an item that's worth a month's game time.
If this person is putting off eating to play they're would be considered "hardcore" in my opinion. And if that's the case, they probably have way to get around the monthly cost, or they could have bought mass time all at once on discount.
I would buy all the enchanting mats below a certain price, buy all the items that rewarded those mats, disenchant everything, then list all the mats much higher than I paid. Bank.