There was a question posed over at The Catholic Forum very recently concerning Jesus' anger in the temple when he saw vendors and money changers taking advantage of the poor (i.e. selling animals - e.g. doves - for sacrifices) and whether selling/buying items from the Piety store (that little shop at the back of churches that sell crucifixes, Rosary beads, medallions, etc.) was the same as what the vendors in the temple were doing, and whether is constituted as the sin of Simony.
Here's where we read about Jesus' anger in the temple:
"And they came to Jerusalem. And he entered the temple and began to drive out those who sold and those who bought in the temple, and he overturned the tables of the money-changers and the seats of those who sold pigeons; and he would not allow any one to carry anything through the temple. And he taught, and said to them, 'Is it not written, `My house shall be called a house of prayer for all the nations'? But you have made it a den of robbers.'" - Mark 11:15-17
Before we address the question, let's read-up on Simony:
"Simony is defined as the buying or selling of spiritual things. To Simon the magician, who wanted to buy the spiritual power he saw at work in the apostles, St. Peter responded: 'Your silver perish with you, because you thought you could obtain God's gift with money!' Peter thus held to the words of Jesus: 'You received without pay, give without pay.' It is impossible to appropriate to oneself spiritual goods and behave toward them as their owner or master, for they have their source in God. One can receive them only from him, without payment." - Catechism of the Catholic Church, par. 2121In short: no, buying or selling items from the Piety store does not constitude the sin of Simony nor does it equate to what Jesus was angered by in the temple (Mark 11:15-17).
Why was Jesus angry? Our Lord was angry because of the blatant wrongdoing being done in the temple. Jesus' concern was for the poor and desperate being taken advantage of, and the temple (note how Jesus expressly calls it "My house...") being used for this sort of business. Imagine if someone had - without your knowing - begun to use your own house/residence as a brothel or some sort of underworld hideout? They say "home is where the heart is" but what if that home had become blackened with the muck of sin? Not only would you not feel comfortable in your house for a while, you'd feel like it has been defiled in some manner and would want it cleansed (cleaned).
Selling/buying religious objects from the piety store at the back of every church is not the same as what took place in the temple that day when Jesus expressed his righetous anger (Mark 11:15-17). Purchashing/selling religious objects is not the same as selling/purchashing a spiritual good such as graces, indulgences, absolution, blessings etc. all of which would constitute the sin of Simony (CCC, par. 2121). For example: it would not be sinful to sell/purchase a set of Rosary beads, but it would be sinful to attempt to sell/purchase the graces/blessings conferred when praying the Rosary.
I hope you've found this helpful.