Amazon offers Fire tablets All-New Fire 7 [amazon.com]
for $29.99 after $20 Off promo FIRE7TAB
or All-New Fire HD 8 [amazon.com]
for $49.99 after $30 Off promo FIRE8TAB
when you use American Express card and select at least $0.01 Membership Rewards points at checkout.
Note your registered American Express card must have membership rewards.
After checking briefly I see expired deal for used tablets with somewhat similar discounts, this is for new tablets.