"Withdrawal fee is 0.0005 BTC" is a mistake on you withdraw-page?
The bitcoin system can take this fee. Ore-mine does not take any fees at all.
The "bitcoin system" can also take lower fees, so there's no need to charge 5x the standard fee if it's really all going into the transaction fee. But a transaction you mentioned in a different post (f57935f7c2ff946670da966953cd0ab7e579b76c431264558d208256ebb05b29) has only a transaction fee of 0.0002, so where did the other 0.0003 of that your withdrawal fee go?