In my best year for points and cash back relative to income I made $60K and put $75K on my AMEX (corporate flying expenses, including hotels at 5% cash back). Any bill I could put on my CC I did. Tried to put a $25K car on it, had the money in my checking account. Minimum cash back was 1.5%. $0 in interest charges, and about $3K cash back.
As long as you treat a credit card like a check, you come out ahead. If you think of a credit card as a revolving line of credit you will pay. But if the people that think that way didn't have credit cards they would be doing payday loans at 20%. There is a reason virtually every company has started excluding CCs from autopay discounts, and it is not because they worry about cost to the customer.