The primary way I justify keeping the CSR is with high spend in general travel (excluding airfare). I have the Platinum card giving me 5x MR on flights, and the free Blue Business Plus card(s) establish a floor of 2x MR earning on everything else (except Apple Pay on the Altitude Reserve, but that would be a whole other post). If I don't have enough points to transfer for a redemption, the discount in award bookings is generally still good enough to make it worth buying miles for 1.5-2 cents each. (ie, I'd happily pay $1830 to buy 122k FlyingBlue miles when they're on sale for 1.5 cents each to redeem for 122k business class round-trip airfare when the cash price is normally $4k.) The main problem with buying miles directly is that there are limits on how many you can purchase each year.

So with the CSR, I treat the 1x extra on travel and dining over the 2x on the BBP as buying miles. So for $250 net cost on the CSR, as long as I am spending at least $17k on dining, rental cars, hotels, and cruises combined each year then I'm effectively buying points for 1.5 cents each or less.

The irony of this game is I agonize more over $250/year spent on a credit card annual fee than I do over dropping $10k on a cruise.