I just checked out the transactions where I withdrew BTC from MPH. It seems like MPH is making a profit of BTC withdrawal fees.
We pay 0.0004 BTC btw.

Here for example https://blockchain.info/tx/e867c97db3c4332965acd73386f674db7d986dd055436dc048353b0fe4c58ee9

The fee of this transaction for 2 recipients is 0.00049671 BTC . 2 recepients paid MPH 0.0008 BTC in withdrawal fees .
A minimum 0.00030329 profit for MPH per payout. Because MPH pays out when at least two people withdraw BTC. I haven't seen one transaction with only one recipient yet in my history.

Here a transaction with 23 recipients from MPH : https://live.blockcypher.com/btc/tx/a75daf5f173ad6ad3dd8207de44acf0fe3c7cc943da5b5c428bd14f8f0b6b92f/

Real Fees are 0.00219887 for this transaction. Fee per recepient would be 0.00009560304347826087.
23 recipients pay 0.0092BTC to MPH in withdrawal fees. MPH pays only 0.00219887 in real fees.
MPH has a profit of 0.00700113 BTC. Wow!

There is definitely room for lowering the fee if MPH wasn't greedy