You can set a minimum bid. If I wanted to sell something say an x1 Danish Greatsword I'd put it at around 150,000. Increment are around 10,000 per bid so the first bidder would be 160,000, 170,000 ect. If people especially want the item, I could see it going for maybe 200,000.
Then, just so your order doesn't get picked up by someone who knows the answer, both of you can PM each other (seller and highest bid) for a price e.g 200,231.