The main problem is people expect wholesale prices to be way under retail. Remember that the wholesale price (for new releases) will be based on the RRP (usally £45-50). Yet because the industry is so competitive, no one sells at RRP. It doesn't matter which wholesaler/Distributer you buy the game from the price will pretty much be the same.
The reason large on line stores can sell them so cheap is because they are happy to make as little as 50p profit per title (Play is a perfect example of this), and they don't have any ebay fees to pay.
Also all the major on line retailers have warehouses in Jersey or Guernsey or Switzerland so are exempt from paying VAT. I also know of some ebay sellers that do the same to dodge paying VAT.
Then there are the promo titles. A title (or group of titles) will be discounted for a period of time. People will buy these in bulk, then sell when the price goes back up (which is what will have happened in the Resent Evil 5 Example).
Some stores just sell titles as loss leaders to build the brand (although this does not happen as often as you may think)
Spend some time researching the industry and how it works. The suppliers are out there. The profits are notoriously small but with hard work and dare I say a little good luck, it is possible to make a living.
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