Optimal reserve prices in auctions may vary with number of bidders.
The optimal reserve price in auctions can change depending on the number of bidders involved. If the virtual valuation function is increasing, the reserve price stays the same regardless of the number of bidders. However, if the virtual valuation is non-monotone, the reserve price increases slightly as the number of bidders goes up. In the end, as the number of bidders approaches infinity, the reserve price reaches the highest regular valuation with zero virtual value.