With all the different prices properties are being listed for, it will be necessary to complete a market analysis on the property you are lookiing to put an offer on. Prior to moving forward, you should locate a buyers agent in your area to ensure the correct research has been completed.
Please contact me with any questions you have as I am a local Real Estate Broker consultant and would be more than happy to assist you with your home buying process.
As others have said; some properties are overpriced to begin with so you really can't determine a purchase price based on a percentage off from the list price.
An experienced local agent would be able to discuss comparable homes that have recently sold in that neighborhood to give you a better idea on what to offer.
I suggest that you interview a few RE agents in your area (if you haven't already) to assist you with your home purchase. The agent will work for you in your best interests to get you the best price possible.
Prudential Connecticut Realty
If you need help finding a expert agent in your area I have many so please don't hesitate to contact me.
If you need help, let me know. I will do some research to find the best agent in your area.
Be well, and good luck!