There's no way to know for sure, but I would surmise from experience that the issue is not necessarily whether the question you get wrong is easy or hard, but
where on the test it appears.
First 1/3 of test = Very Important - The test makes huge adjustments in your score based on your answers.
Second 1/3 of test = Moderately Important - The test makes moderate adjustments in your score based on your answers.
Final 1/3 of test = Barely Important - Just make sure that you finish all the questions. At this point you are only fine-tuning your score, which is mostly decided already.
Getting an easy question wrong might appear to have a larger impact on your score than getting a hard question wrong, but this could be because of its location instead of its difficulty level. A hard question must be "earned" with several correct answers, but you might see an easy question after getting just one question wrong. The GMAT penalizes you severely for getting multiple questions in a row incorrect, and thus the easy question appears to be the culprit, when it has more to do with the fact that it's the 2nd question of the test and thus has a huge impact on your score.
If you get an easy question wrong early in the test, then that could take a long while to recover from, since the GMAT algorithm makes larger adjustments early in the test, thus impacting your score more. Whereas a hard question wrong later in the test, after you've already done well and thus earned yourself yet another hard question, is unlikely to make much of a dent in your score.
Conversely, if you get an easy question wrong later in the test (assuming it's not an experimental question), then it's because you're not doing well already, and this should not affect your score much.
To me, the answer seems to be that an easy question CAN be worth more points than a hard question, but not BECAUSE it's easy or hard. The real issue is QUESTION LOCATION: where the questions happen to appear chronologically.