To buy things cheaper, look at epic/rare objects before patch day (late at night^^) search for sales like:
Watever
start price: 90G
Direct Price: 200G
Time remaining: 2-8 hours or less
Bet & wait until patch is finished, look at your mailbox
Use it or sell it:
Watever
start price: 200G
Direct Price: 200G (or higher)
ps: sorry for my english, i don't know the corrects terms for start price etc...^^