In 40 years of reloading, I have found 5 pieces of fired 41 mag brass at a range. In 40 years, I've hung out at lot of ranges.
As a hard core brassaholic, my wife has ordered me to only bring home the brass I fired. I have never bought a box of 44 mag ammo, but do have 1600 loaded rounds sitting on the shelf. The shed holds 19 gallons of polished and tumbled 45 ACP. I no longer pickup 9 MM or 40 S&W brass because there is no storage space left.
Yup -- 41 mag brass is scarce.