I am trying to calculate cell L2 (spend_above_frequency) which is sum of the entire column J minus K2.
Essentially, I want to calculate column L based on columns J(sum) and K(minus one instance/cell value of K).

You will need to get the frequency_bucket to be sorted though correctly. So I would look to split on the β_β and take the second part of it casted to a integer.

parseInt(split(frequency_bucket,β_β,2))

Although one thing I notice is that you have 30+ which would throw an error. So I would then do this.