Sort:  

It's because the price of STEEM is going down (or was... its about the same since few days). I saw the post money going up (without extra votes) when the price was rising. It works both ways.
You can see it Account value too. It all changes with the change of Steem - goes down or up.

Coin Marketplace

STEEM 0.25
TRX 0.20
JST 0.038
BTC 94129.96
ETH 3496.79
USDT 1.00
SBD 3.78