For the month of October you are able to get a free $15 voucher for the PSN store when you do a top up for $80 via PayPal. This equals a 15.89% saving.
You may process the top up via their browser store or on your Playstation 3, 4 or Vita console. You will then receive a voucher code to the primary account holders email address which must be redeemed before 30/11/2014.
UPDATE: As per GravyNanna's post, this deal isn't invitation only.
Spoke with Playstation support again (always an enjoyable experience - not). I have been told that they are still trying to deal with it and to "sit tight you will get your money". Knowing what the answer would be I asked if they could just refund my $80 then, which was a "unfortunately no". I raised the 30 November expiry date in original terms and conditions to activate voucher and was told that there would be a new expiry date once the codes are all sent.
I can lodge a complaint via the support@playstation option through the website if I wish. I'll decide whether it is worth my time soon or I will just "sit tight" for a couple of weeks and see.