True. Deposits minus Withdrawals = net income for MA.
However the old saga that began when Marco claimed that MA made their money from decay is to be taken with a ton of salt on top. The reason is the relation you stated; less money can be withdrawn.
No "portion" of decay goes into MA's pockets, whatever they might have claimed. It's simply impossible. They made their income from the deposit in the first place, they can't create more income by taking another cut from the same deposit.
In MA's financial reports they state the ingame amount of PED as an *something*
(forgot the name) liability that doesn't count into the balance sheet, because of their unclear state (will they be withdrawn or not? MA can't tell so they don't put it up as a normal liability).
Auction fees is essentially decay.
Anyway. My point was that if player A has no CLDs and 100 PED, and player B has one CLD and 100 PED. The next week they have 100 and 105 PED respectively. Is player B likely to withdraw those extra 5 PED? No, he's going to spend it inside the game. So even if MA "gave" him a "cut" from their income, they really didn't. They only gave him a few virtual digits that he might convert to real money some day. It's only when he withdraws as they have to live up to their promise and give him his cut. Which will not happen because a week later they both have 0 PED left.