Who Is The Grinch At Wal-Mart?

Wal-Mart is one of the few companies out there that will match other competitors prices.
For instance, Wal-Mart sells bananas at 57 cents a pound and Albertson's (a grocery store chain) and they sell it for 33 cents a pound.  If the customer mentions the price at Albertson's price, we will sell the bananas at the lower price.
90% of the time, the customers are honest and there is no dispute.
It's the other 10% who are a problem.
Recently, a guy was banned for life from all Wal-Marts because he got upset when they didn't match his prices he sought.
Well, there are people out there who lie about the prices of the competition.  Some people supposedly memorize the prices of 20-30 items.
Some people will wait for the cashier to ring up the price and then say, "Oh, wait a minute the price at Albertson's is this" after they see the price.
Other's will try and buy a larger item at a the price of a smaller price.
Many others of the dishonest will just make up a price that is so ridiculous that it's obvious they are lying.  For instance, a guy wanted to buy Accent seasoning salt, which our price is $3.48 and tried to get the salt for $.64 each.  The guy probably tried to buy the seasoning salt and then sell them to another retailer for about $3 and make a nice profit.  That sale needlessly to say, didn't go through.
When cashiering, I usually don't challenge a customer and their price unless the price is 50% or more off than our price.  We have a list of the local grocery store advertisements, so we can check it out, if needed.
Now the dilemma:
Some people are really poor and may need the savings, but do you call them on a matched price, especially if they are lying?
Some will say, what difference does it make?  Wal-Mart makes billions of dollars in profit a year, they can afford it a couple dollars here and there.
The problem with that argument is that the money also comes out the pocket of the Wal-Mart employees at that store. 
Each Wal-Mart store has a profit sharing program for it's employees and the more price matching there, the lower profit for the store and lower the paycheck every 3 months for it's employees.  An extra $300-400 every three months sure comes in handy.  So, those who lie on price matching are taking money from the Wal-Mart store employees.
So, here is the question as who is the Grinch:
The people who lie to get a discount of a few dollars?
Or the Wal-Mart employees who say no to the liars and get to increase the store's profits and increase their own paycheck every 3 months?
For me, I stick with honest people and don't mind saying no to the dishonest people, though if a person is on food stamps, I may give them a break.
So, am I Grinch or the customers?