Open Question: Advice for bidding on a house?

We're ready to make a bid on a house. Our absolute highest bid can only be $4,000 under the sellers asking price, plus closing costs. Are there any good strategies for bidding less without offending them? Background on the seller's possible motivation, or lack of motivation: - They bought this house over a decade ago, and even with our highest bid (less than what they are asking), they will still be making a large profit. - They are renting it out - It's only been on the market for around a week, but we are the only interested party as of yet Any suggestions??