You need to take into consideration that 1 SBD is 2$. If someone sends you 1 SBD, you need to upvote with a 4$ vote value. Then the receiver will have at least twice as much value back or more.

As it is in the moment the receiver can be assured to gain 10%-50% value. That dwindles down to 10% depending on the voting power that you use up.

You can check the values here https://steemworld.org/@cryptokraze.