This thread is very informative on your chances of carrying off a heist stealing this cube.
Conclusion: Low, unless you're willing to take only a fraction of the face value.
Thinking through it though - you might be able to get away with spending the cash overseas, where it will take some time indeed for the money to be under scrutiny by banks to see if the serial numbers are out of circulation. There's then problem of getting the money there without anyone noticing, then there's the problem of what kind of characters you're going to be defrauding overseas.
All told - probably a better idea is to use all that cleverness to make a 1.5 million dollars the good old fashioned way: Spending a few years saying, "Nothing from my end" on Zoom calls.
Conclusion: Low, unless you're willing to take only a fraction of the face value.
Thinking through it though - you might be able to get away with spending the cash overseas, where it will take some time indeed for the money to be under scrutiny by banks to see if the serial numbers are out of circulation. There's then problem of getting the money there without anyone noticing, then there's the problem of what kind of characters you're going to be defrauding overseas.
All told - probably a better idea is to use all that cleverness to make a 1.5 million dollars the good old fashioned way: Spending a few years saying, "Nothing from my end" on Zoom calls.