The victorian era had the division of people into the noble upper class, middle class and the working class.
Algernon's display of cucumber sandwiches was referred to as reckless extravagance in a young person by Jack. But the irony here is that cucumber sandwiches are not even extravagant or reckless to serve at tea. Another is the fact that the lady that the sandwiches were meant for is not even a young person.
We have the hypocrisy of algernon who scolds jack for trying to take a sandwich but yet does so himself. He even ends up eating it all before lady Bracknell arrives. Then he has his servant lie that there were no cucumbers at the market.
The lady's reaction is that of indifference about the sandwiches. A great part of this play explores the consequences of the reckless formalities of society. Jack considered as rash behavior, the formal extravagance of the upper class.
