I don't understand your concern. If I was trying to sell something, that's exactly what I'd do.
Set fair price - This is the arguable part, what is fair but it's the seller's property so...
No bites? Lower price a little, wait a little, repeat until sold.
Bump topic after it is buried under new posts. This keeps active listings towards the top and lets finished listings depreciate to the bottom.
I suppose you could report topics that aren't following the rules for that forum, or you could suggest new rules for that forum, though I wouldn't hold my breath on that as whatever rule you want, someone else is bound to be opposed to it.