Here is the Mathematics :-

I dedicated 15 Steem to MB
I get 0.005-0.009 SBD every day from my allocation.

If i put the average daily pay out 0.007 SBD then in 365 days i get 0.007 * 365 =
2.5 SBD

For 15 Steem Power i had to invest around 20 SBD so in 10 Years I can recover my investment and reap in profit.

It might look like a very meagre profit to you but if you consider that fact that without the allocation that Steem Power would stay idle in my account because of the allocation I am getting something as incentive for holding my Steem Power and not cashing it out.