Some products on Amazon cost MORE on Amazon Prime, Even For Prime Members!

Earlier today I was looking to purchase an item on Amazon.
(2x VonHaus Vertical Wall Mount Bike Cycle Storage Hooks to be specific)

I found them for £7.99 – available next day, on Prime.
However, I noticed it was available £1 less in the “other sellers” bit.
Curious, I took a look:

Both same product
Both same vendor

Prime was however £1 more.

This was despite me being a Prime member (~£70 a year) AND being logged in to my account.
So why do I need to pay a further premium to have this item delivered via Prime?

This is happening more and more with Amazon.
Coupled with a LOT of items no longer available next day (which was the original ’sell’ for Prime) – it’s suddenly becoming apparent that Prime, isn’t that, well, Prime!