Whats wrong with Blizzards own gametime online store ;D? i pay about 9.5€ / Month.
Sure you maybe save a euro or two on it but. Not to much to actually bother about imo, as i really have no idea when i dont feel like playing WoW anymore. By that i mean, i play in periods. Sometimes i play for about 3-5months and sometimes i wait about 3months til i play it again. So dont want to waste that extra month on it

Well, just my tought on it.