The "To Keep Up" Wiki

From and thank you to: https://www.makeuseof.com/amazon-prime-cheaper/

If you buy a Gift of Prime membership, pay it in full and upfront, and send it to yourself, you can activate it whenever you want. So you can start using it months after Amazon Prime's recently announced price hike goes into effect.

How to Exploit the Hack

1. Head over to the Gift of Prime page on Amazon and buy a full Prime membership for $119 (you will still have to pay taxes on top). Send the gift to yourself. When the e-mail for gifted membership arrives in your inbox, let it stay there until your current membership expires.
2. Head to Prime Memberships under your account (top-right corner) and turn off auto-renew. This will ensure Amazon doesn't automatically renew your subscription. This is important because automatic renewal will charge you the new higher price.
3. When your Prime membership expires, activate your “gifted” Prime membership. Just like that, you get to stay on the old $119 rate.