As far as I understand it, the valuation of a post in $ is kinda average, as it isn't exact before payoff is reached (running average of STEEM, that is quite volatile lately).
That $ amount shown includes the curation rewards of those who voted on the posts and this the half of it.
Then, only some part of the remaining is liquid, the other comes as SP.
If STEEM >= $0.25, we receive SBD as rewards, otherwise STEEM only.
So, getting liquid 29 STEEM from a $29 post sounds about right to me, of course, for the moment.
We have to work to get STEEM above $0.25 to get more, as SBD is usually > $1.
Have a great day!