Perhaps Irix cine lenses at less than $1300 each, SLR Magic APO EF lenses at $1200 each, and upcoming Meike full-frame cine lenses has something to do with it?
If only Sigma would follow suit 🤞
you didn’t specify which camera you use, but here’s a cage for Sony:
https://www.bhphotovideo.com/c/product/1449314-REG/smallrig_2238_arca_qr_half_cage.html