Im not following your logic Herby

I never said to get rid of cards from fair or lab for that fact.
I just said get rid of tavern and use the Royal Arena like HR to get hero cards

The revenue would still come by gems used to get over cool downs buy chips etc to power up
They could add in a daily reset like HR
They could make it so once you do win the card you still need to pay for it with credits - so once again revenue from buying credits with gems

Lots of possibilities for revenue exist. I do not see spinning in the tavern and getting that magical hero card once ever 20-40 m credits as a big revenue maker, especially with Tavern Tuesday - where many of us spend 90% or more of our credits that we use in tavern on Tuesdays and spin very little the rest of the week.

So if done properly this could be a huge revenue stream.