The problem is that you convert it to USD or BTC. But CAT is undervalued and is expeceted to raise in price. Then you'd make the same like with DOGE or even more. It's speculation
How much CAT should I get in one day with ~500Kh/s? Is there a calculator? I know of Dustcoin.
Could be, but don't think so
Calculator: http://cat.nonstopmine.com/calculator/ (but it's with the old diff so you should divide the amount of coins by three)
Edit: At the moment you would make about $3-4 with 500 kh/s so it's definitely not worth it. That's why the price has to raise.