A big company starts to sell their soul, whatever the consequences (2,3,5)
I believe the answer is:
at all costs
'whatever the consequences' is the definition.
(I've seen this before)
'a big company starts to sell their soul' is the wordplay.
'big' becomes 'tall'.
'company' becomes 'co' (abbreviation).
'starts to' says to take the initial letters.
The initial letters of 'sell their soul' is 'sts'.
'a'+'tall'+'co'+'sts'='AT ALL COSTS'
(Other definitions for at all costs that I've seen before include "whatever may happen" , "Regardless of expense" , "come what may" , "Regardless of what needs to be paid" , "Whatever the consequences" .)