EA website Item database for recent sales. Another good one for your reserves only is
http://www.mutmanager.com/load.php
You see realtime sales and they provide an average sale price. You click the card for more detail and can see the high and low. I usually post for 1/3 higher than the average price and stuff sells in about an hour. Or you can post for 24 hours at near the highest most recent sale amount. You may make more in the log run but I like to clear my reserves as fast as possible.
I was able to make 900k this last weekend just by farming Ultimate Legend players. Did Brooks, Lewis, and Reed each under 300k. Turned around sold for 550k - 700k. Was able to turn GT McCoy into Boss Brooks. Went from 900k on Friday to 1.9m on Sunday morning.
http://www.muthead.com/forums/madden...or-coins-guide