A contract is formed when there is a "meeting of the minds", e.g., when both parties are in agreement. You make an offer - if they accept, then it is a contract. If they counter, then that is a counter-offer - if you accept the counter-offer then it is a contract. Unless both parties agree, no contract is formed. That is how contract law works.Sure, but isn’t a greentoe bid a commitment to purchase (sure, you can get out of it, but that’s extra work)? So you have to spend several iterations increasing your bid from a reasonable low starting point until one closes down the spread.
Also, I am suggesting that the used (definitely) overseas (maybe) prices are good datapoints to anchor the starting point for bids.
From GreenToe's FAQ: (https://www.greentoe.com/faq)
"When you place your offer you are agreeing to buy the item at the price you have entered."
"We guarantee that any counter offer you receive will be valid for at least 24 hours."
So you are only agreeing to buy at the price you enter. If a counter-offer is not to your liking, you can just let it lapse - there is no obligation to buy.