There is certainly a tradition of being able to buy items at holy places and having them blessed to take home. My mother used to have a fancy glass bottle (purchased in gift shop) that had been filled with water from Lourdes (free, not purchased) and then blessed during a service there. I have a rosary (purchased) that was blessed at a Papal audience (no charge). So the physical items had a price, but the blessings did not.

I would be quite suspicious of anything advertised as already blessed, as the only blessing involved might be of the scam artist's pocket.