our boat had it as an option, but we bought our boat used, and the previous owner did not get it. ours has a lip all the way around it where the cushion would go. so i just cut a piece of 5/8" plywood to the shape using a jig saw and painted it (no cushon though) just as a temp thing so we can throw wakeskates and backpacks under it when the racks are full and without losing any room.
We had custom cover made over at tower Bimini's and at the same time we had them make an actual cushion up there, and it turned out awesome. looks like its meant to be there. we have a ton of room up in the bow, so we had them make it in two pieces since its such a large area so we can store it in the back compartments in separate pieces if we don't use it. but we just leave it up there all the time now, one of my favorite additions to the boat. more storage+ more seating=an awesome addition.
i don't remember exactly how much it cost to do, since we had several things done at the same time. but i believe it only cost a little over 100$.(i may be wrong though). awesome price considering how great it looks.