Billy: That's the wrong question.
Because the listing price does not necessarily reflect either: (1) what the home is worth, or (2) what other people might be willing to pay for it.
Let's take those one at a time.
What a home is worth: You're assuming, incorrectly, that a homeowner (and his/her agent) knows about what a home is worth, then marks it up a certain amount--say 5%. Sometimes that's how it used to be done. But no longer. First, with the mix of conventional sales, short sales, and foreclosures, three similar homes may have three very different price tags. Second, there are different strategies for selling a home. Regular home sellers might tend to price the property at or slightly above what they think it's worth. Investors who've rehabbed a property want a quick sale and often will price the property about 5% below what they think similar properties should sell for. Some short sales and foreclosures are priced substantially below market, with the anticipation of a bidding war raising the final sales price to, or even above, comparable sales.
What other people are willing to pay for it: Lots of people act on emotion. In the example above, with properties priced well below the comps, bidding wars can drive a price surprisingly high. So don't assume that the listing price reflects what people might pay. It could be higher or lower.
Bottom line: Basing your offer on the listing price is a poor idea.
How should you make an offer?
Find out what the house is really, truly worth. (That's also important when it comes to getting funding. If you make an offer that's too high and the house doesn't appraise for that amount, you won't get a mortgage.) Ask your agent to do a CMA on the property. And make sure you also look at all the other comprable properties currently on the market. (Comps reflect properties sold within the past 90 days. Allowing for a 45-60 day closing, that means some comps might have gone under contract 5 or more months ago.)
Once you know about what the house is worth, you and your agent should come up with a strategy. Do you want to make a "best and final" offer near the top of the range? Or, if you're not in love with the house and hope to get a bargain, do you make an offer moderately below the comps?
Notice that you're making an offer based on the value of the home, your interest in it, and a strategy that may best achieve your goals. Nowhere in the process did you (or should you) begin from the listing price.
Hope that helps.