Last time I observed this I was getting the exact same item that I bought being advertised to me constantly, across multiple sites. No variation at all. It was a pair of hiking shoes. If it had then offered me hiking poles or rain coats or anything else that would have been useful, but instead it was the same pair of shoes I had already purchased.

If the ad network had actually suggested useful paired items that i dont already own, then those ads should actually stand out, as they are actually relevant to me.

If its not cost efficient to actually target to the individual (and I dont doubt that it isn't), im not sure what Paypal is bringing to the table here that Amazon etc can't already do.