Cheapest it has ever been.
You need US PSN Account to redeem.
PlayStation®4 Voucher Redemption Instructions.
Open a Sony Network Entertainment account on PSN (or use your existing Sony Entertainment Network account).
Select the PlayStation®Store icon on the PS4™ system home screen.
On PlayStation®Store, select 'Redeem Codes' at the bottom of the menu.
Enter the code.
Once the code has been entered correctly, select 'Continue' on the dialog box.
Select 'Confirm' to accept the Trial Code Terms of Service.
Select 'Continue' to complete code redemption
geez getting cheaper and cheaper. Feel ripped off paying $20 now lol