Jake Kucheck is absolutely right. The odds are EXTREMELY strong that you over estimated ARV and/or underestimated repair costs. EVERY single new wholesaler/investor I've ever worked with does it. Its the reason why newbie wholesalers get such a bad reputation. Its because they THINK they know what they are doing but the reality is they DON'T. Experience is king in this business.
Out of tens of thousands of offers and hundreds and hundreds of deals, I can only think of 2 houses that a private seller's "asking" price was below my desired offer price. I played the reluctant buyer on both (as outlined by others), but I was definitely not leaving that house without a contract.
Now I have seen banks put REO's on the MLS cheap to create a frenzy, as Will Barnard mentioned, and it works. But I've never seen a homeowner smart enough to work investors like that.
Bill Gulley, you pretty much outlined the MAO formula in your post about how you used to do it in the old days. Its just with doing it hundreds of times, you can begin to estimate the holding costs, resell costs, and desired profit as a general percentage (30% of resell value or ARV).
I used to do exactly what you outlined, Bill, and when I first came across the 70% of ARV minus repairs formula I figured out that the vast majority of the time it matched with my more intensive calculations. BUT it was a whole lot faster and easier to figure.
Now depending on how experienced you are and on different factors of the deal, that 30% discount breaks down something like 10-15% to resell (realtors, holding costs, and closing costs to buy and sell) and 15-20% profit. Obviously you then need to factor repair costs out of the formula too.
Now on higher end properties many times I will factor only resell costs as a percentage and determine a flat figure for profit. I'm normally willing to buy a $200K house for far less than a 20% or $40K profit.
Keep in mind that the 70% formula or its derivatives only works if you are trying to resell to a rehab to retailer. Landlords don't normally use a formula like this to determine if a house is a deal or not. They will use some type of income and/or expense calculation. I always ask my investor buyers what their "magic" formula is. They normally have a formula of their own to determine if a house is a deal or not and I want to know it.