Aggie,
The bigger the property price it's likely there is a bigger discount and profit. For example, using your 83% discount of FMV if a property value is $80,000 then a lender may be willing to take $66,400 for the property. Now you didn't just make $13,600 in profit because out of this you must consider your closing costs, holding costs, loan costs, realtor costs etc.
However, this same scenario on a property that's valued at $425,000 looks quite different. You could potentially purchase the property for $352,750 and take out your expenses and have a profit.
There are too many variables however, such as what you can reasonably sell the home for, and much of the time the loan that the seller has can give you some insight on how much a lender is willing to discount. If the loan has PMI that adds a layer of difficulty to the sale. Also, there are lenders that won't discount at all from the BPO price so there is no profit margin for you.
I like to shoot for $20,000-$30,000 profit but if I end up with less, I won't cry. There are times we make under $5000 profit which is a lot of work for that little money. The big picture is to get the deal done though so I'm not crying over little profit.