In the high limit room at Bally's in Vegas are a bank of slots that pay Total Rewards tier credits at twice the rate of normal. So for every $5 coin-in, you get 2 TC instead of 1 TC.
We played that middle one today for a while and found it to be surprisingly playable. We racked up about 700 TC and lost about $200 playing $5/spin.
Not sure if other props have these, Paris didn't. Bally's HL is usually pretty dead so maybe they're trying spice it up.