My understanding is that there is no entry fee for overnight visitors because this is covered in the overnight hotel tax.
So there will barely be an entry fee for people coming for the day too. For a measure targeting people coming from thousands of kilometers away, I do not see how this is even going to make a dent in the tourist influx.
Looking for relatively similar cases like Machu Picchu or Tanzania national parks, I would have expected a fee between 50$ and 100$ to curb the tourism.