You're deceiving the whole purpose of an auction IMO. Auctions are always timebased and not pricebased.

If you're looking for a price of $15 or more - then start the auction at $15 and let the increment go on from there after setting a specific timeframe. Or better yet, specify a reserve.

Looking for a price of $15 and starting the bidding at $1 actually means fooling your prospective clients. In an auction - every single bid counts. So if you started at $1 - even a $3 bid could win this.