that's one on me

that's one on me

That is a mistake or joke that makes me look rather foolish. It's just normal gasoline? The guy down the road said it would clean my engine, charged me double for it. I guess that's one on me. I can't believe I fell for that—that's one on me!
See also: on, one
Farlex Dictionary of Idioms.

that's one on me

That's a joke at my expense, as in And after all that discussion they didn't show up-that's one on me. This phrase must be distinguished from that's a new one on me, which means "this is the first time I've heard of or seen that" (as in A checkerboard rug-that's a new one on me). Both idioms can be used with other personal pronouns (for example, that's one on you) and date from the early 1900s.
See also: on, one
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • a fool and his money are soon parted
  • fool and his money are soon parted
  • fool and his money are soon parted, a
  • parted
  • cost (someone) dearly
  • dearly
  • doofus
  • (there's) no fool like an old fool
  • be (not) (one's) bag
  • experience is the teacher of fools