I go to the Casino approx 2-3 times a year with friends and every time I go I see the same 3 people at the poker tables. Not at the same table but they are always there playing poker no matter what day or time I go at. And the max buy in at these tables is 100 dollars and these three guys always have thousands worth of chips. So I assume they are pros who play poker for a living. Its literally their job to sit at the tables and grind grind grind. So to answer your question, I would say the casino.