Need negotiating help

[Logan Allec]

Monthly Rent: $5,100
Asking Price on MLS: $830,000 (originally listed in October 2014 for $800,000)
Price that can work for me: $720,000 (this is a hot part of Los Angeles - definitely no 2%/1% rule here).

Do I go in at $700,000?  I feel that that number may be offensive.  However, the seller does not know I have seen the listing on MLS/know his asking price on his listing.  He just thinks I am responding to his voicemail, which he left in response to my yellow letter, so he may not be so offended.