The credit card companies still get paid on transaction fees, which is where your rewards come from. They collect $150 from the merchant and pass $75 on to you.

The credit card companies still get paid on transaction fees, which is where your rewards come from. They collect $150 from the merchant and pass $75 on to you. They are arguably making just as much money on you as someone with low transaction volume (say $250/mo) but with a $3k-$5k balance @ 20% APR which is $50 to $80 in interest a month.