If I was the person you were trading with I would be quite upset. If you cant manage to figure out a trades value then don't trade.
God I hate these threads.
Bury me alive, bury me with pride
Bury me with berries, that forbidden fruit and cherry wine
Thank you berry much, but tonight's my night and I'm Barry Bonds
Swingin' for the fences, barbaric Kendrick in idle time