Father Z: If you sell a sacred thing which was blessed with a constitutive blessing, it loses its blessing and must be reblessed or reconsecrated.

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.

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