If I were to sell an item at auction and the item didn't sell for the amount I wanted, I have two options. I can keep re-listing it for the same amount and hope that someone comes along that wants to buy it.
Or, I can re-list the auction for the highest bid price that was reached at the earlier auction, in the hopes that whoever bid highest still wants the item, and I can at least sell the item (albeit for less than I originally wanted).
I'm not sure if this qualifies as shill bidding. From a seller's perspective it sounds like common sense. It's fairly common to calibrate prices based on demand. I often tell my wife, when she's posting items on ... wherever she posts them ... is she pricing at her perceived value? Or pricing to sell?
In any case, an auction, almost by definition, isn't a marketplace where you go to expect "bro pricing".
I would recommend the OP post a 'want to buy' thread in the pipe forums where pricing tends to follow perceived community norms more closely than an auction site that favors "top" over "fair" pricing. I intentionally put "fair" in quotation marks because we're talking about money.