The fact that it succeeds does not mean that you get the money back (eg the price of monero could drop if that happens). You may also have miscalculated some parameters in all this or something unexpected happens (where human factor is involved). So there should always be risk involved imo. Otherwise I agree, even in a probability 1 success situation this would still not be called "cheap".

Agreed, no such thing as a real-world investment with truly 0 risk.