the estimation on website should be wrong. because I have seen someone getting >50000 ROI daily with only 50kH/s. but the total emission rate is just 86400 = 120 x 720 coins daily.
If it is that easy to get a coin, it will be worthless.
You are reading it wrong or you are reading it from wrong place. Yes, 50 KH/S is very high HR and usually it's Nicehash or something like Polaris CPU. It still shows 25000 coins as expected daily income but you can count on half of that. That's from my experience. Also, 50KH/s is half the HR of entire pool. Who can afford that speed?