Shimon turned the page of the newspaper that he was holding, and let the paper rest against the counter, in front of him. The clang of the store bell drew his attention away from the sports section, and onto the two young men who had just entered the store. "We’d like to buy a mezuza," they informed Shimon. "Can you show us something high quality, mehadrin?"
"Of course, of course." Shimon responded. The customers’ impeccable Hebrew accent was not lost on Shimon. He hurried to find them what they were looking for. "Here, a mehadrin level mezuza. That will be four hundred shekel."
The young men paid, happily took their new purchase, and walked out of the store.
A half hour later, another man walked in. He was neatly dressed in an expensive suit. "Can you help me find a mezuza?" he inquired, in heavily accented, halting Hebrew. "I would like one that is mehadrin."
"I’ll be happy to help you!" Shimon replied. He took out a mezuza and showed it to the man. "This is a high quality mezuza. For you, I’ll sell it to you for two thousand shekel."
The man reached into his wallet, and withdrew his credit card. Shimon swiped the card, delicately placed the mezuza in a bag, and handed it to the man. With profuse blessings for a safe flight home, Shimon escorted the customer to the door.
After the customer had left, Chaim, Shimon’s assistant, looked up from the pile of books that he was placing on a shelf. "Uh, Shimon, just wondering. Weren’t the two mezuzot that you just sold basically the same in quality? Why were the prices so different?"
"Yeah, yeah, they were more or less the same," Shimon admitted. "But I’m a businessman! Why shouldn’t I maximize my profit, where I can? Just look at that guy! Clearly he has more than enough money. Besides, I’m doing him a favor. He’s getting the great merit of spending a lot of money on mitzvot!"
Was Shimon allowed to act as he did?
Rabbi Asher Weiss, shlita:
Shimon transgressed the prohibition of "geneivat da’at" (i.e. deception). It also appears that he transgressed "ona’at mamon" (fraud) and actual theft. If the customer had known that he was buying an item which he could have purchased for a third or quarter of the price, and the price was raised only due to his presumed naiveté, he would not have concluded the purchase.
To my great distress, this is not an uncommon phenomenon, particularly with regard to the sale of lulav and etrog, and the sale of Torah scrolls. In one particularly painful situation, I discovered that a wealthy Russian Jew requested that a particular Israeli Jew purchase a Torah scroll on his behalf. The Israeli middleman asked the Russian Jew to pay $85,000 for a Torah scroll which the middleman had purchased from the scribe for only $55,000. This is a severe transgression. There is no doubt that, if the purchaser had known that the middleman was taking such a high commission, the purchaser would have found a different middleman.
Shimon’s argument, that he is assisting the customer in fulfilling the mitzva of paying a lot for a mitzva object, is not valid at all. The task of spending money to beautify a mitzva is the customer’s responsibility, not Shimon’s, and, therefore, there is no license for Shimon to lie and deceive a customer, for this purpose.
In the past, it was established that if someone sold an object for more than one sixth of the going rate, the sale was invalid. Nowadays, it is difficult to uphold this law, because, for most items, it is unclear what the going rate is. Someone who buys an item in a higher end store will often pay more for a particular object than he would in another store. Nonetheless, even nowadays, if someone triples or quadruples a price, the sale has a status of "mekach ta’ut" (transaction based on a mistaken premise), and is therefore invalid.
In summary: Shimon violated the transgression of ‘deception,’ and, seemingly, the transgression of actual theft, as well.