We use this expression to say that we are not impressed or surprised by something.
You can use this phrase in ………… language.
A: I’ve been working for ten hours without stopping!
B: Big deal! My brother who’s a firefighter sometimes works 48 hours without a break.
A: They’re offering three for the price of two on Slevomat.
B: Big deal – on the internet you can find the same stuff for 75% cheaper anyway.