Yeah I found conflicting opinions on it. Too murky for me to sort out. Even the Magisterium AI waffled between "ok to sell blessed rosaries if only to cover costs" and "absolutely can't sell rosaries specifically". IDK.
I'm not sure where you are finding blessed things for sale but I've never seen that in my experience. All blessed objects I've found are only given away for free, and non-blessed things are for actual sale.