I won six total, but also I won two magic workshops, and I maybe this week I will get another one.
I use a lot the Law of Attraction with the Spire, and I have four spire sets, plus a ton of extras (I am in Whynador if you want to check) I normally do only until the 1st part of 2nd floor (where my FS rewards arrive.) Otherwise, I would have parted with the Spire already. However, even if I do not want more big prices in the Spire, it keeps on dropping. For example, this week upon doing the first fragment of the second floor, and call it a week... look what happened (so, it is not like leaving now this part undone.)
Yes, two purple chests, out of four battles... and I get a ton of chests yellow, purple, and some of the more common blue, and the bosses usually drop library pieces or magic stuff (and I have 3 50% PP rotting... as I almost don't need them, and I have over 100 of 10% ones.
Edit: And I said this in multiple post, visualize yourself with the rewards, plan for room in your city for your desire drop here, assume you will get it, feel you have it already, plan with it... and the Spire will get loose, loose, loose... trust me... now, it can't stop dropping rares.
Edit next day: I got a genie (the first genie ever, despite getting several magic buildings and spire pieces) from the first purple chest, and a blue one spawned with a tree. Waiting for the gate to open to access the other purple chest.
(And thinking of finishing the floor, I need a magic workshop and possibly I can manifest it, and get it from the boss. The trick is to press click, and only let go of the button when you feel "now what I need will drop.") Will update the second purple.
Edit Again: Three teleports in the second one, not as exciting, but still nice.