EVE Online has this interesting currency called PLEX (Pilot's License EXtension). One PLEX can be bought from the EVE Online website for $19.99, and you can trade it for in-game currency, or cash it in for 30 days of game time. PLEX allows players to essentially buy ISK (EVE's in-game currency) with real-world money, or buy gametime with ISK. This keeps away the gold-farmers, which we can all agree is a good thing.
Up until September 16th, you can buy a pack of 13 PLEX for $199.99, which is a savings of $59.88. If you're a hardcore EVE player and you're planning on buying a lot of ISK soon, this would be a good time to do it. 13 PLEX could sell for around 5 billion ISK right now, which is a small fortune.