http://forums.backpack.tf/index.php?/topic/6033-new-unusual-price-suggestion-guide-the-cheat-sheet/

copypasted:

Buyouts (B/Os)

B/Os alone cannot be used to make an unusual suggestion. Just like we don't like to use offers as the only proof to raise the value on an item, we don't like using B/Os alone to drop the value as this has frequently caused bp.tf to lead the market with consecutive suggestions every 1-2 weeks dropping the hat (see Miami Wraith). This also creates an issue when future suggestions use those values as proof when they are still inaccurate.

​​Exceptions: There are rarely situations where we feel B/Os can be used as the only proof in a suggestion. We will accept such suggestions ONLY if there are literally no usable sales in the last 2 months. In these situations, the suggester must show proof of recent sales and why they are not usable (quicksell, sold for more unpriced hats, etc.). In these cases, there is frequently a large buyer-seller gap and dropping the value based on B/Os might actually result in a few sales that could then be used to refine the value.

How you should use B/Os: All of this does not mean that B/Os are not useful. Use B/Os to give a general sense of your range. If a hat remains unsold for 2 weeks with a B/O of 2 buds, a sale at 3 is probably an outlier. Use them to check whether your suggested range makes sense. Just don't use them as the only proof to set both your range.