I think chase sapphire reserve was the peak at $1,500 bonus (assuming you were already going to travel) in exchange a $450 fee, but that was offset by $100 global entry credit and a few other benefits, so it was close to $1,500 free for many people I know. I know my wife and I got it, and it was basically $3k for free.

It was so costly that Chase had to list mention it specifically in their 10-K and I believe all the other banks looked and it and said no way are we spending that much.