Not totally that tbh. It depends on your board. I was able to go to as low as 650 coupons per shisui frags. For example, in the board you showed, you have way more items that are "common" than "rare". This means these drop more often and lower the drop rate for shisui. Normal dust, magatama, bells, stamina potion and mood scroll are considered "common" items iirc.

Before I'm asked to share, here's the board I had. Of course, I did quite a few refresh to get this board. So it really goes down to how many refresh you do and how badly you want to play with RNG.