This looks interesting indeed

[atx840]

I think you are missing a key piece to this.

If someone pays me a buyers premium of $20, I'm up $20 for my efforts.

If my daughter wins and doesnt pay me the $20, (highly likely as she is 3 and always broke) I'm out my $20. She saves on the front but together we are even, so now she has to flip them for more then the cost plus the $20 I'm out. Not always easy to do.

So if HOC wins and doesnt pay H&S, H&S are out 20% of the previous bid, as that was a guaranteed BP to be paid before HOC bid up. Now who know if HOC hadnt bid up if someone else would. That's their biggest risk if it's borderline a good price, loose the BP and make it on the flip.

Now if HOC slowly bumps up that BP managing their risk on not winning too many lots then they can create a significant amount of profit for H&S to compensate for the lots they do win and have to flip. Now celing bids, if ones been entered it likely could be accessed but I won't go there.