Eastbay has select Nike Game Day jerseys on sale. Most players are $49.99 but some, like the Brady red alternate jersey, are $79.99.
To receive 15% off your $49 purchase, enter promotional code SEPT15 at checkout. Order value must total $49 or more before services, taxes, and shipping & handling. To receive 20% off your $99 purchase, enter promotional code SEPT20 at checkout. Order value must total $99 or more before services, taxes, and shipping & handling. To receive 25% off your $199 purchase, enter promotional code SEPT25 at checkout. Note: SEP Codes Expired, see below for OCT discount codes
This appears to not work for all players so YMMV.
Shipping is free.
EDIT: Appears LKSOCT10 works for 10% off and LKSOCT15 works for 15% off $100 or more. So not as slick as codes above, but still saves some.
FFOCT15 works for 15% off $75+