If the problem is computationally difficult, then it is a mistake to not count the value of computation.

Suppose you believe that a reasonably smart person with some spare time can make money on the stock market. There is still a question of how much money, compared to the amount they could earn doing other things. If we pick some reasonable value for intelligent, market understanding thought, then we can define a new value $α *$ which is $α$ - the value of the time it took to find.

The value of thought time, compute time and data are all constant. The returns are linear until you get to the point where you disrupt the market, destroying the pattern. Thus $α *$ is much harder to get if the amount of money you have to invest is small. (Especially if you don't bet the farm.)