We use this expression ironically when we are not very happy about something.
You can use this phrase in ………… language.
A: Sorry, Paul. There aren’t any comfy chairs left so you’ll have to sit on the floor.
B: Thanks a bunch.
A: Have you seen my sandwich?
B: Ah! I found one on the table so I threw it away. I thought you had finished.
A: Thanks a bunch! That was my lunch.