Why are you offering such small amounts if bitcoin's price is so much right now.
Nobody is wanting to send 0.004btc worth of bitcoin to have to pay nearly 0.0008btc of that in transaction fees to ensure that it is sent properly and in a timely fashion. As far as I know a send of more than 0.01btc takes 0.0002btc minimum to send to get it to the buyer in less than 45 minutes.
That would be just silly in flushing away the exchange amount doing this for such a low of an amount.