Sooner or later promoted listings become a zero sum matter. If everyone's doing it, nobody's doing it and it's a cliff the company fall over.
Back in the day buckets of third party commerce sites went with featured listings, seller naturally want grab visibility, up their price covering expense and bam... Zero sum, then all the sites did away with it.
The formula that works is quite simple, one listing, all sellers offers shown along with front line information(s) as to the specificity of items given conditions. Amazon they call it "The race to the bottom" to capture best pricing.
Buyers want get what they order as described at the lowest price, end of story.
Now Amazon favors some stuff too so does Walmart, "Buy Box" in fact Amazon being sued in the UK for a billion bucks due to the Buy Box. Folks assuming that means they get the best deal, not so.
IMHO it's something eBay should consider or even consider as an aside aggregate to the current listing system. Buyers can look at things now as they do or click a button and presto, there's all the offerings in one listing and that way they've time to measure up the two against each other.
They could still have promoted listings (offers) appear at the top of the single listing. Perhaps even go as far albeit I wouldn't recommend it as having a Buy Box whereby that can be bought.
