Ok, I think in that case my argument doesn't work. Let me try another approach.

Suppose some stranger appears to you and says that you're living in a simulated world. Out in the real world there is another simulation that contains 3^^^^3 identical copies of a utopian Earth-like planet plus another 3^^^^3 identical copies of a less utopian (but still pretty good) planet.

Now, if you press this button, you'll turn X of the utopian planets into copies of the less utopian planet, where X is a 10^100 digit random number. (Note that K(X) is of order 10^100 which is much larger than K(3^^^^3) and so pressing the button would increase the Kolmogorov complexity of that simulated world by about 10^100.)

What does your proposed utility function say you should do (how much would you pay to either press the button or prevent it being pressed), and why?