Several readers have sent similar questions about the selling of sacred things. I will simply answer rather than post excerpts of the questions.
Let’s start with the most sacred of all, the Eucharist. Selling the Eucharist would be a terrible sacrilege. The Code of Canon Law for the Latin Church uses the word “nefas” (“really really really bad”, “intolerable”). The Eucharist is sacred in Itself. If you sell the Eucharist, you incur automatically an excommunication. The lifting of the censure is reserved to the Holy See or a confessor with a faculty from the Holy See.
Selling a relic also has he word “nefas” applied to it in the Code. Relics are sacred things in themselves, because they are the remains of saints or blesseds or, if they are not part of the body, were objects associated with the saint. If they are sold, they remain holy things.
Selling blessed objects is not necessarily a sin. There are various decent reasons why one would sell a blessed object. There are bad reasons as well. Some things, such as statues or things of various age or artistic merit will have great monetary value. Other things have a particular rareness or association which makes them valuable, even though they in themselves are not much to look at.
Selling of sacred offices is also a sin and a crime in the Church’s law, for obvious reasons.
Selling of “smaller things”. When I go to a religious goods store, people will sometimes ask me to bless things such as small statues, rosaries, books, medals, etc. I am happy to do so, but only after they have been purchased. If you sell a sacred thing which was blessed with a constitutive blessing, it loses its blessing and must be reblessed or reconsecrated. If I were to sell my, for example, chalice which was consecrated by the late Card. Mayer, the purchaser would have to have it reconsecrated. The same would go for a rosary. However, there is no question of “reblessing” something like relics of Sts. Nunilo and Alodia rescued from Ebay or a flee market: relics are sacred in themselves. The reliquary, however, would be duly reblessed.
I hope that helps a little.