"Some times you can't see the forest through the trees......."
Ok, so it was a Idiom, or Idiomatic Expresssion, and those can vary depending on the culture. In this case the OP (in England?) wrote "an arm and leg buyer" which is not a commonly used expression in the US.
In America, IME, it's more often written as "it cost me (or they charged me) an arm and a leg".
Trivia: when I was in College (a long time ago) there were a group of students from Eastern Europe who's mother tonque was not English, but they had been taught Oxford English, so sounded like they were from England, with an accent.
One of their goals while studying in the US was to learn American English, including idiomatic expressions ie: so they could sound more like Americans (they were from Russia). Very interesting.
BTW: I'm currently at my cabin surrounded by a bunch of vertical semi-flexible poles that sway in the wind. They also have a rough grey/brown/reddish exterior which is covered in long narrow green spikes that form an almost conical shape going from the bottom to top of the pole which gets narrower as it gets closer to the top??