The value of the token, SPI, will increase to reflect the returns. The first re-evaluation was done at 10K token sales, when the price of SPI tokens increased from 1 STEEM each to 1.1 STEEM each (if bought directly from @spinvest) and 1.12 STEEM each through Steem-Engine.
You absolutely could do the same thing yourself - power up sufficient STEEM and lease for 20% returns. If you did it yourself, it would be the case that you would not have to consider 3rd party token risks.