Your calculation is quite a good calculation and I´m thinking about it in the same way.
BUT, there is one important thing which you don´t add to calculation.

There will be lot of user which never reach withdrawal minimum.  How much it will be for doge? 1000 ... 10000 ... more?
There will be lot of user which just stop using faucet.
There will be lot of user which can be banned from many reasons.

This can decrease amount of crypto which will be needed to pay.
It is no problem to add some strange condition for users to be able to withdraw.


But as you say...somebody from Rollercoin must give correct answer to this because more and more users with brain start thinking about site that this is scam and stop use it.

So rollercoin boys give as answer please .