Sometimes, there isn't a "before" price. Let's say someone bought the house for $500,000 in 2005. They fall behind on payments. Meanwhile, the house is now only worth $350,000. Sometimes you'll see a pattern--it'll be listed for $500,000. Then, when it doesn't sell at that price, the owners will attempt a short sale at $350,000. If it doesn't sell then, and gets foreclosed on, it'll come back on the market...often/usually for less than $350,000. But it really depends on the BPO provided to the lender. Now, realistically, the BPO should take into consideration the fact that the house had been listed for $350,000 and hadn't sold. Therefore, it's worth less than $350,000. But BPOs aren't always accurate.
In other cases, though, the owners won't go through that whole process of attempted sale. They may have talked to a Realtor who provided a CMA showing the price drop, and the owners may simply have stopped making mortgage payments. So you don't have that pricing history.
And maybe when the market strengthens, it could be possible to see a house actually put on the market for more than had been asked for it pre-foreclosure. But, in today's market, generally the price of a foreclosed home will be lower than what was asked pre-foreclosure.