There is a question as to whether or not items blessed by a Catholic deacon, priest, bishop, or pope may be sold. The answer is YES. However, it must be noted, that when a blessed item is sold, the blessing is lost. Therefore, if someone were to sell an item that was blessed by the pope, for example, the blessing would be lost. The person who purchases the item would not have an item blessed by the pope as the blessing would be lost. Blessings can never be sold. Even if the seller explicitely states that the blessing is not being sold, it is still lost. The blessing cannot be passed on if the item is sold, traded, or bartered. To imply that the blessing continues after the sale is simony and fraud. You cannot ever buy, trade for, or barter for a blessed item and still retain the blessing.
Now, what about "Papal Blessings" obtained from Rome? In this case the person obtaining the blessing is paying for the parchment of declaration, packing and shipping, and any administrative fees. Remember, the people involved in producing the document and packing and shipping it must be paid. There is no charge for the blessing per se. Any fee is to pay those involved in the process of procuring and sending the document.
Any religious article purchased never comes with a blessing. You must get it blessed after the purchase has been completed. If you want something blessed by the pope, after the transaction is complete, ask the dealer to have it blessed and then sent to you. If the dealer is reputible they will either say they are unable to do so or will do so but tell you that it will take added time.
If a donation is given for a blessed item the blessing is retained. However, it must be a legitimate donation and cannot be for a specified amount above the items cost to the dealer. For example, a dealer pays $5.00 for a rosary and has the rosary blessed by the pope at a general audience by an agent. The dealer can ask for a minimum donation of $5.00 plus his actual shipping and handling costs but no more than that. You are free to give more, but are in no way required to do so. If there is any profit made on the transaction the blessing is lost.
If you have an item blessed you may give it to anyone and the blessing is retained. If you buy a Miraculous Medal as a gift and, before giving it, have it blessed by a priest, the blessing is retained. Any blessed item may be given to another person, whether that person is Catholic or not, and the blessing is retained. The exception to this is for items blessed under the old regulations on indulgences. These blessings have all been abolished. These blessings were personal and do not pass on to another person if the item is given as a gift. So, if someone were to give you an old indulgenced crucifix or rosary you would not be able to gain the indulgences. The item is, however, still considered blessed in the ordinary sense.
Added September 20, 2007. There are dealers on eBay who claim that this is not true, that the Vatican knows about the practice of selling blessed items, and that the greater price is because someone has to take the items and get them blessed, etc. This is misleading information. What I have written is according to the norms of the Codex Jurex Canonici 1984 (The Code of Canon Law of 1984). I am a Roman Catholic Priest who has studied Canon Law and Moral Theology. I am not in competition with these unscrupulous dealers. I am only interested in presenting the truth and saving people from being defrauded. If you question what I have written, then do the research yourself. The Code of Canon Law, in English and Latin, is available online as are sites where you can contact canon lawyers.
As a further note, an item blessed by the pope is no different than an item blessed by any Catholic deacon, priest, or bishop. There are no longer any reserved blessings of religious articles. Religious articles do not carry the Apostolic Blessing. That can only be given to a person and can be imparted by any Catholic priest or bishop provided the one receiving the blessing has fulfilled the requirements. Religious articles blessed by the pope do not have any special power. To believe that they do is superstition, a sin against the First Commandment. Having an item that was blessed by the pope has a purely sentimental value and no other. It is a souvenir or a remembrance from Rome, nothing more.
No Catholic may bid on, purchase, or sell an item "blessed by the pope" without commiting sin. In the case of dealers who are aware of what they are doing the matter is grevious and the sin is mortal. In the case of buyers and bidders it is safe to assume the sin is not grevious and the sin is venial.