$6,000 is about 4 months' supermarket spend for me.
Wowzers.
I put ~$35k on it two years in a row, and only netted ~1.7% cash back each year, which was an overall loss considering the citi double cash rewards. I used it for any and every purchase, and did not change spending habits. I ended up downgrading to the free version when I got the gold card.
Probably get burned on this too, as I'm already struggling to find a valuable way to cash out 100k points.