I used to work for an auction in the 80s, and still attend many. One of the most popular auctioneers I see, has said that "if you see my ring men bidding, they are customers too"...…. sometimes the auctioneer wants something in the sale for themselves and is the fairest way to gauge a fair price. but yeah I agree, I have seen the same thing, someone in the audience bidding against themselves basically.... or someone "planted" in the audience to "jack the bid" over an unannounced reserve. I've been asked to do that myself, I don't/won't.