No, There is no mana, like there is no steempower.

There are vests and resource credits. When I vote I lose voting power and resource credits. Both are used to limit my ability to receive vests as rewards proportional aligned with how much vests I have as steempower.

Steem is deposited in the steem vesting fund. The only way in is to buy steem with fiat. When you power up the steem is put in the steem vesting fund and you receive your share of vests as steempower.

SBD is a convertible note, a promise to receive 1 USD worth of steem out of the steem vesting fund through conversion. The steem is still locked in the steem vesting fund. hint

If I choose 100% payout you receive vests, if you choose 50%-50% you receive vests and a promise(SBD).

The costs are "resource credits" proportional aligned with how much vests I own.

Through the use of dynamic fractional reserves we all pay for transaction costs.

It limits the ability to receive rewards.

A user would have to earn rewards at an 8.45% rate to combat (inflation/dilution) just to break even after paying for these transaction costs...

Read the fuk-king whitepaper. :)