Not very. Auctions are competitive sales and people don't bid logically. Lots of people see a rare whatever sell, then assume their common one is worth that. Other times a common whatever will sell for a ridiculous amount because two idiots decide to compare penis and wallet sizes, simply don't care what it costs because they need gratification, or are willing to pay above average market because it's an item not available near them.
Never trade guns unless you're honestly trading and know both what you're getting and what you're giving.
Never trade guns unless you're honestly trading and know both what you're getting and what you're giving.