There are tons of stadium events auctions on ebay after an auction for Stadium Events and 4 other NES games sold for $13,105. Many of these auctions are for a game that is not that rare!
There is a NTSC Stadium Events which was released in the USA and quickly discontinued and is the more expensive version. There is a PAL Stadium Events too, which was released in Europe and is not as rare or expensive. Below is a buying guide so you know how to tell which Stadium Events version is which and don't get ripped off.
NTSC Stadium Events: Expensive Version
The NTSC Stadium Events is the more valuable and more rare version of the game. It sells for anywhere from $1,000 for just the game and $13,000 for the complete game with the box and instructions. Here's how you tell if the game is NTSC.
1. "Stadium Events" is written on one line on the cartridge
2. Nintendo Seal is a circle on the box and on the cartridge
3. The words on the packaging are always English (some PAL versions are English too)
See historic NTSC Stadium Events prices
PAL Stadium Events: Cheap Version
The PAL Stadium Events is still a fairly rare game and pretty expensive too, but not compared to the NTSC Stadium Events. The PAL version sells for about $100 for the cartridge only to about $1,000 with the box and instructions.
1. "Stadium Events" is written on two lines on the cartridge
2. Nintendo Seal is oval shaped on the box and cartridge
3. The words on the packaging might be in German, Dutch or another language
See historic PAL Stadium Events prices