Some buyers will instruct their Realtor to deliver a "low-ball" (well below list price) offer for a property purchase. This practice can be effective if the seller signs the deal back ---keeps negotiating ---and doesn't get annoyed or ignore the offer. It is the legal responsibility of the Seller's realtor to present them the offer, whether they like it or not.
I have made these offers when we have special insight into the sellers circumstances... sometimes when the listing agent or client speaks about their situation with people they should not. ---nosey neighbors, co-workers, family members that just can't keep quiet. ---and the seller needs to move for work, is bridge-financing, divorcing, just inherited some money, etc. These types of circumstances may suggest that the need to sell is real, and waiting is working against the Seller.
I just negotiated a deal where our offer price was 30% lower than the asking price. The low offer was the basis for an aggressive negotiation that left our buyer happy, and with more money to do upgrades and renovations when they moved in. In turn, the Seller is happy to have sold their home, and move on with their relocation plan.
I have been on the receiving end of a "low-ball" offer, and HOW the offer is structured matters much more than the dollar amount. In general, the question of a low offer is whether or not it is in GOOD FAITH. Does the buyer client really hope to purchase the property, or is this just testing for a rock-bottom deal? An offer to purchase that is laced with extra clauses and conditions should not be well below list price if the Seller is to take it seriously. The best low-ball offers have few conditions and will make the Seller think long and hard about accepting it.