Bought ps4 back buttons attachment from the Sega Sykes seller for £29 plus 5 shipping I think so price was good, as close to RRP as possible compared to other sellers overcharging. It came quickly - on the ealier scale of the estimated delivery time. Package was new and properly sealed as expected.
Product is official product by Sony and exclusively for ps4, it is good solid quality. Buttons click nicely and are very responsive and erganomic.
It will take time to adjust to using back buttons if it is your first time.