Good point. However, why would the dictator put on the charade and try to keep his status/power unless he valued it more than the wealth he could obtain by opening the country up? If the gains are small, this is probably a good margin to look irrational on, but if the gains are large enough, opening up outweighs the irrational act (on this margin). There are plenty of other things to appear irrational about with lower stakes. You don't have to appear kooky about every single decision you make in order to convince others that you are kooky - just enough of them.

So in a nutshell, if the difference in standards of living for the dictator under the two scenarios are large enough, the irrationality ploy shouldn't matter (much).