Sounds like a very short lived offer, I hate flash sales, I had an email informing me circa £50 will be taken from my card in January, I may cancel and wait for an offer. Feels horrific value compared to GPU.
It was only for lapsed or new subscriptions anyway.
ShopTo have it for under £42, or you can buy discounted wallet top-ups and pay that way. Paying by card for anything on the PS Store is a terrible idea.