As a customer it is bad management not to have a product available, but often it is either bad stock planning or they are just trying to get rid of a particular product. I have seen this before at a SS pub. Other managers have tried to sell the Wheat beer and Pure Brew at a discount as it was running out of date.
I do know another non SS pub that sells bitter at a pound a pint on occasions and only to get rid of it. As other pubs in the area are Weatherspoons and SS. Not sure this is good, as it still states outside that it's 2.45 a pint.