I like to share my friend's (F) recent transaction. He was a professional negotiator/arbitrator for some time before jumping in RE. 

He offered 210K cash for a property to a large wholesaler (WS) who was advertising it for 225K. WS emailed promptly to call him within the hour or someone else may take the deal. F deliberately emails to say he is dealing with an emergency but will call before noon (a few hours later). 

F calls and WS claims she need 220 to accept the offer and if he can revise the offer, F stays firm and the call ends quickly presumably the deal was secured with someone else. A week later, WS calls back congratulating F since the "other buyer" could not close. 

F thanks for the call, and politely confirms that he has moved on but is willing to pay 200K as his interest has dwindled. WS clearly pissed off, claims they have a huge list (which they probably do) and will sell it no time and was doing F a favor and allowing him the opportunity. F stays firm and the call ends on not so positive note due to WS's feeling that she is being cheated. 

WS calls 10 days later stating that since he is able to pay cash they reconsidered and willing to accept 200K. F being a trooper he is, offers 185K because he really would be buying for his non-existing son so he can get some experience. WS, if she could, would choke F with he bare hands. After much wrangling, F relents at 188K and a deal was struck. 

You must be prepared to walk away from the deal.