A bought the cloud hash rate with a 540-day service period. When expired, he only gets the corresponding amount of FIL.
B bought SFIL which can mine perpetually. After 540 days, he can choose to continue mining or sell SFIL in the secondary market.
In this case, B gets FIL and the additional revenue by selling SFIL. Then, you'll realize that holding SFIL is almost close to zero-cost mining.
Moreover, with the development of the FIL hashrate ecosystem, SFIL's price will be much higher than your buying price. In addition to receiving free FIL, you can also enjoy other benefits brought by the development of the Filecoin Ecosystem. This is impossible to achieve with all existing cloud hash rate products.