You have complete thought error in your calculation. First of all:
2.13$ Vote minus curation:
2.13 * 0.75 = 1.6$ (keep in mind that this can change depending on when you vote on your post)
1.6 * 0.75 = 1.2$ of this vote is given to you as SBD. SBD is currently worth 9.5$ on Bittrex
1.6 * 0.25 = 0.4$ of this vote is given to you as STEEMPOWER. STEEMPOWER is currently worth 3.3$ on Bittrex.
1.2 SBD * 9.5 = 11.4 USD
0.4 SP * 3.3 = 1.32 USD
11.4 + 1.32 = 12.72 USD
You paid 3 STEEM for this upvote: 3 * 3.3 = 9.9
12.72 - 9.9 = 2.82 USD PROFIT.
'1.6 * 0.75 = 1.2$ of this vote is given to you as SBD. SBD is currently worth 9.5$ on Bittrex'
This is totally and utterly false, it's 1.6 x 0.5 given as SBD.
Do you not look at your own rewards and compare them with the $ author reward amount on the posts??
Also, do you not see the little selection box below where you type with rewards : Default (50%/50%) ?
Also, you may have noticed that your steem power rewards haven't been 25% lately either.....
.