I have one to add to this for those interested.
ufi4nymdn
As stated, it's $10 a minimum purchase of $79 at the Razer Store, valid through May 31, 2013.
Awesome, thanks for this! I used 9D4AP-TVKX8-B8K9I-G0F7N
The 5 invite keys I got:
8464H-UTGVJ-X6JDF-2LM75
G44JL-VH24G-BRK2S-985K0
493WH-XJ6K2-QI1A9-1D0UU
K67LT-EWZUV-227CF-8L2CW
SD6V5-MJVO2-7VNWR-QPISJ