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WHSmith has admitted it made more than £700 by selling single tubes of toothpaste for £7.99 in a hospital.
The Pinderfields Hospital branch in Wakefield was caught selling Colgate, normally priced at £2.49, by a visitor.
The retailer blamed a pricing error and said proceeds from the sales would be donated to charity St George's Crypt.
In 2015, WHSmith was accused of exploiting hospital customers after the BBC found it was charging less on the high street.
The retailer said 89 tubes of toothpaste had been sold in the Pinderfields shop while they were priced at £7.99.
A spokeswoman said: "We would like to apologise to our customers for a recent pricing error in our system relating to this product."
She added: "The error has been rectified and changed to the correct price of £2.49."
The BBC investigation in 2015 found that people were paying 89p more for a 750ml bottle of water and £1.50 for an A4 refill pad at Pinderfields compared to a store in Leeds.
After pressure from Dewsbury MP Paula Sheriff, the firm said it would match stationery prices and cut food and drink costs.
St George's Crypt, which is based in Leeds, provides support to homeless, vulnerable and people suffering from addiction.