Anyone that really knows anything about real estate has a good Idea of what a property is really worth. Right now we have alot of unmotivated sellers that just list with a big price hoping to find a fool. A correctly priced property in this current market won't last but a few days. As an example let's say there is a house that among the knowledgable real estate people its deemed to be worth 300k. The unmotivated seller prices it at 400k to catch someone napping. The seller willing to negotiate prices it at 325k. Realistic seller prices at 300k and stands firm. Desperate seller prices it at 275k and the fool price it lower than that. The sub 300k listing will probably be sold an hour before list or even before. The question is where are you offering in this spectrum? Are you offering 300k on the 325 listing or you offering 250k on the 300k listing?
I understand all to well that your offer has to meet your financial criteria but the problem seems that your criteria dosent match the market and sellers might view you as a bottom feeder that isnt worthy of consideration.
As has been alluded to earlier, if you want to low ball in this market, make a all cash offer with proof of funds. Large earnest money deposit, no contingency and 10 day close. This puts you way ahead of the iffers and maybe and those that need a third party to actually provide the funds.